E-text prepared by Emmy and the Online Distributed Proofreading Team
(http://www.pgdp.net) from page images generously made available by
Internet Archive (http://archive.org)

      See 43683-h.htm or 43683-h.zip:
      (http://www.gutenberg.org/files/43683/43683-h/43683-h.htm)
      or
      (http://www.gutenberg.org/files/43683/43683-h.zip)

      http://archive.org/details/ouryoungaeroplan00port

[Illustration: THE FIGHT IN THE AIR. _Page 42._

_Our Young Aeroplane Scouts In Germany._]

OUR YOUNG AEROPLANE SCOUTS IN GERMANY

Or

Winning the Iron Cross

by

HORACE PORTER

Author of
"Our Young Aeroplane Scouts In France and Belgium."
"Our Young Aeroplane Scouts In Turkey."
"Our Young Aeroplane Scouts In Russia."

[Illustration: A. L. BURT COMPANY]

NEW YORK

Copyright, 1915
By A. L. Burt Company

OUR YOUNG AEROPLANE SCOUTS IN GERMANY

CONTENTS

        I. SAVED BY QUICK WIT             3
       II. A STIRRING HOLIDAY            13
      III. A THRILLING MOMENT            23
       IV. THE STOLEN PAPERS             34
        V. WHEN THE LIGHTS WENT OUT      45
       VI. A FLYING VICTORY              56
      VII. THE RAIN OF BOMBS             67
     VIII. ALONG THE BATTLE LINE         78
       IX. THE LUMINOUS KITE             90
        X. THE CARRIER PIGEONS          101
       XI. UNDER THE RED ROOF           112
      XII. THROUGH FIRE AND FOG         123
     XIII. CAPTURED BY COSSACKS         135
      XIV. A WONDERFUL RESCUE           146
       XV. DUEL TO THE DEATH            157
      XVI. DRAWN FROM THE DEPTHS        168
     XVII. A MIGHTY STONE ROLLER        179
    XVIII. TRAILS THAT CROSSED          190
      XIX. RABBIT'S FOOT FOR LUCK       200
       XX. WINNING OF THE IRON CROSS    210
      XXI. HELD IN WARSAW               219
     XXII. AN HOUR TOO SOON             229
    XXIII. A LEAP FOR LIBERTY           238
     XXIV. AGAIN THEY WON OUT           248

OUR YOUNG AEROPLANE SCOUTS IN GERMANY.

CHAPTER I.

SAVED BY QUICK WIT.

"HOLD on there, I want a word with you!"

Billy Barry and Henri Trouville, the Boy Aviators, were in the act of
climbing into a superb military biplane on the great parade ground at
Hamburg when thus hailed by a mild looking man in citizen's attire,
with face half-hidden by a slouch hat and a pair of huge, horn-rimmed
spectacles.

There was a note of authority in that voice, gently tuned as it was,
and behind those spectacles were a pair of eyes as keen as gimlet
points.

The speaker was none other than Roque, the noted secret agent--"Herr
Roque," if you please, fitting into his masquerade as a merchant having
contract business with the authorities of the canvas city of aëroplane
hangars.

"Come over to quarters for a few moments, young sirs, won't you?"

The polite manner of request was for the benefit of the bystanders, who
had been awaiting the flying exhibit, but the slight gesture that went
with the words indicated a command to Billy and Henri.

They knew Roque!

Heinrich Hume, aviation lieutenant, who usually had a good deal to say
on those grounds, made no more protest than a clam at this interruption
of a special aëroplane test. He simply waved two other aviators on
duty into the machine, as Billy and Henri marched meekly away with the
imitation merchant.

While many of the spectators marveled at the apparent breach of
discipline, the lieutenant was content to let them wonder. At least, he
offered no explanation.

Billy and Henri did a lot of thinking as they crossed the parade
ground--there must be something brewing, or Roque would not have been
so impatient as to invade the parade ground at the time he did.

Roque conducted the boys into Lieutenant Hume's private office at
headquarters, closed and locked the door behind them.

Removing his spectacles, and throwing his slouch hat among the maps
that littered a big table in the center of the room, the secret agent
at the same time changed his form of address--the oily manner was
succeeded by abrupt and stern speech, which showed the real man of
brain and unlimited authority.

The secret agent had seated himself, without invitation to the boys
to do likewise. They stood, facing the real Roque they knew by former
experience.

"Where is Ardelle?"

Roque put the question like a pistol shot, and fiercely eyed the
youngsters before him.

The point-blank query failed to reach the mark intended.

Billy looked at Henri and Henri looked at Billy, and then they both
looked at Roque with never even a quiver of an eyelash. They had not
comprehended what was behind the dreaded agent's snapshot at their
nerves. The truth of the matter was, they did not know anybody by the
name of "Ardelle."

So Billy, with a bold front, remarked: "You can't prove it by us, sir.
Mr. Ardelle is not in our list of friends."

"None of that!"

Roque pointed a menacing finger at the astonished pair of youngsters.

"I have it beyond doubt that Ardelle was on these very grounds a day or
two ago, and by the word of a man who could not be mistaken. Fool that
he was not to be sure at the time, and only the garb of a sailor to
mislead him."

Then it jointly dawned upon the minds of Billy and Henri that Anglin,
the smiling secretary of the eminent director of affairs at Calais,
and later in the rôle of a bubbling sailor here in faraway Hamburg,
must be the Ardelle about whom Roque was talking.

They realized, too, that through their boyish delight in lending aid
and a helping hand to one they had known in intimate association with
that best of friends in France, they had unconsciously maneuvered
themselves into a dangerous game, a slip in which meant a dance with
death.

A tissue message from this very suspect that Roque was so eager to
apprehend even then burned against the breast of Henri, a little wad of
paper that now represented the price of the world to a pair of bright
boys.

Condemned of mixing in the battle of wits between the grim Roque and
his strongest wily rival from over the sea, and it were better that the
young aviators had tumbled from their aëroplane during the last high
flight.

But those who traveled in spirit with Billy Barry, the boy from Bangor,
Maine, U. S. A., and his plucky teammate, Henri Trouville, in France
and Belgium, can assure that it is no easy task to catch this pair
napping.

The courage tempered by that first and continuous baptism of fire was
good steel for any emergency.

Roque owned to himself that his quickfire had failed to get results.
His informant, himself just returning from a secret mission on hostile
soil, had noted the movements of the sailor suspect on the aviation
exhibit day, and also the attitude of Henri at the moment when the
message was passed. But of the message itself, the reporting agent
could have no knowledge. He was not near enough to detect a trick so
deftly done.

Roque and Ardelle had measured brains many a time and often, but
heretofore at long range, and the former had never seen the latter in
person. Had such been the case, the French agent's invasion of the
empire would have ended at Bremen, when these two masters of craft had
both been guests at the same time of the same café.

Roque's unerring judgment had convinced him after the first question
that the boys had no knowledge of the name Ardelle. Their first
profession of ignorance was too real to be mere acting. The boys took
care that the light that came to them as Roque proceeded did not shine
in the direction of the lynx-eyed questioner.

The rigid lines in the face of the secret agent relaxed. These boys,
after all, had once served him a good turn, with a skill, courage and
fidelity far beyond the ordinary, and, perhaps, he was not sorry that
he had apparently found them guiltless.

"Now, young sirs," said Roque, resuming the manner of the merchant, "I
have another little journey in store for you. I don't know for certain
that it will prove as exciting as the last jaunt we took together, when
you located a shipload of guns for me, but maybe so, maybe so.

"After we have made our excuses to the lieutenant," he continued, "we
will go over to my humble home in the city, where I have some new
clothes for you. I do not think you are warlike enough to want to
travel in any sort of uniform, especially with a simple tradesman like
myself."

It was on the tip of Billy's tongue to ask Roque why he kept up that
sort of talk with those who knew him without his mask, and when there
was no purpose to be served, but Billy concluded that he had better let
well enough alone.

A roomy carryall was in waiting at the further end of the parade
ground, toward which the merry old merchant led his young friends, with
a hand under the elbows of both. It was pardonable for the aviation
lieutenant to grin when the trio were passing, after making their
excuses.

It had not, however, occurred to Henri to smile a response. He was just
then indulging in a cold perspiration, caused by a leaping thought that
Roque might personally supervise their change of garments, and in that
curious way of his light upon the tissue billet pinned on the inside of
his (Henri's) shirt-front.

Because they had not fully understood the meaning of the dimly dashed
message, Billy had suggested that they keep it for another sitting. The
paper wad had not then turned into a torpedo.

Roque's house might have belonged to a retired gardener rather than
to the man with the iron grip who claimed it as home. The dooryard
blazed with red flowers, and the well-kept lawn was lined by earth beds
spangled with blooms in colors beyond count.

"Welcome, young sirs."

Roque waved the way into a wide hall, at the end of which yawned a
great fireplace. Bowing before them the boys saw the tallest man they
had ever met outside of a sideshow, a very giant, who wore a long gray
coat, with a good day's output for a button factory in front.

"This is my man of business, young sirs--Paul Zorn."

The "young sirs" instantly formed the opinion that Zorn would have no
trouble in cracking a cocoanut between the row of glittering teeth he
displayed when Roque so introduced him.

"We are going to put our young friends into store clothes, Paul. I hope
you will be able to properly fit them, and it will also be my care that
you do."

"Confound the man," thought Henri, "he has never since he called me
out of the machine shifted his eye long enough for me to get a hand on
that tissue, and now he's going to act as my valet. He's just full of
suspicion."

Billy, also, had been figuring some in his mind just what would break
loose if Roque should find the sailor's note in Henri's possession.
All of the powers of argument this side of the North Sea would then
avail nothing in the matter of convincing Roque that he had not been
double-crossed.

The only crumb of comfort that Billy felt he could hope for if the drop
fell was that Roque would quit his comedy acting behind the scenes
for the once--but that was scant comfort, surely, under this cloud of
anxiety.

The boys soon knew what Roque had meant by "store clothes," for
it was a regular storehouse of the styles of all nations that the
makeup magician maintained in the second floor back of his Hamburg
home--uniforms galore, the garb of the fighting man in the Old World
war, known under the folds of Britain's Union Jack, the Tricolor of
France, the black double-headed eagle of Russia, the sable Cross of the
German Empire; the attire of the dandy civilian, the sedate tradesman,
the student, the clerk, the livery of house and carriage service, and,
indeed, what not?

"A nice little collection, young sirs," observed Roque, which remark
again prompted the giant Zorn to display his mouthful of shining
molars.

"How do you think Paul would look in this outfit?"

Roque indicated on the display rack a regulation English uniform of
olive drab, with puttees, and a cap of the traditional French arms
shape, but of khaki color.

Even if the boys had been in the mood to say that Zorn would look like
the Eiffel tower in any sort of uniform, Roque gave them no time to
break in upon his humor.

"Nothing like keeping up-to-date, young sirs, in my business. It was
only a few weeks ago that this new style French soldier first appeared
in Havre. And here we can make his mate in a minute or two."

This cat and mouse play was wearing on Billy and Henri. Free of
anxiety, they might have enjoyed digging into the maze of disguises as
they would the pages of a popular detective story, but they had a play
of their own to make, and no chance yet to make it.

"Now, Paul, how will we fix up these young flyers for a bit of ground
work? Something plain, yet neat, I think, will do for the sons of
Doctor Blitz--I am Blitz to-morrow, I believe, Paul?"

Zorn simply showed his teeth. He was not expected to answer.

"Now, my bird boys, get out of those uniforms and I'll make a pair of
likely students out of you. Do you prefer Heidelberg, the School of
Arts, or the Conservatory? No matter, though, it is just a shift for a
short journey, and I guess I can make you up to pass muster."

All the time Roque was chatting principally for the amusement of
himself and Paul, his hands were busy sorting a pile of clothing and he
was ready to start a couple of young Blitzes into society in the most
finished style--from glazed cap to shiny shoes.

It was just at this moment that Billy was seized suddenly with a fit of
laughter, and his high glee was directed at Henri.

"Won't you set 'em going in that layout!" he howled.

With that he made a jump for his chum, as if to hurry the process
of transformation. The playful effort commenced at the throat and
scattered a few buttons. Henri resisted the attack, and for a second or
two held Billy in close arm lock--time enough for the assailant to get
a pin-jab in the thumb, and a wad of tissue paper in the clench of four
fingers!

Roque viewed the antics with a frown of impatience, but the assistant
of grenadier size roared his approval of the fun.

Henri was brisk enough then in taking off the old for the new, and by
the time Billy commanded attention there was no occasion for worry.

Billy had swallowed the tissue!

CHAPTER II.

A STIRRING HOLIDAY.

TO be rudely routed out of a snug nest in a feather bed at 3 o'clock
in the morning--a morning with a real chill in it--is not a desirable
experience for the average house-bred boy, and even such seasoned
campaigners as Billy Barry and Henri Trouville were inclined to grumble
when the giant Zorn yanked the covers from their downy couch and
gruffly ordered them to get up and dress, and to make haste about it.

By the pale gleam of a couple of candles, and the slight warmth from a
newly kindled fire in a white china stove, the "Blitz boys" made their
toilets of the interesting characters they were to assume.

"What time is it anyway?" yawned Henri.

"I guess I'm not good enough in higher mathematics to figure it out for
you," growled Billy, as he tussled with leather shoestrings that tied,
he said, "seven ways for Sunday."

The voice of "Dr. Blitz" sounded at the foot of the stairway, in the
lower regions of the house. There was no "young sirs" about it. The
"good merchant of Hamburg" was on vacation.

"Crawl lively there, you snails," were the words that ascended.

"Wonder what tip he is working on now?" whispered Billy.

"You will never know until you get to it." Henri had before been
impressed with the fact that Roque was not in the habit of springing
until he got on the board.

"Good morning, Dr. Blitz," was Billy's cheery greeting to the man who
was making hasty breakfast at a table drawn up before a crackling fire
in a big brick cavern. He could not have testified from side view that
it was Roque, so he took a chance on "Blitz."

Along with a gulp of coffee the imposing person addressed shot a remark
in German over his shoulder, which Henri afterward explained to Billy
was very near to profanity.

The boys edged into chairs at the table, but missed a round of muffins
through staring at the "doctor."

The merchant masquerade was wholly outclassed by this new display of
the make-up art.

Billy wanted to say "ring the night bell," but sheer admiration kept
him silent.

Whether it was the combined effects of the steaming coffee, hot
muffins, and a big black cigar that followed, or the silent tribute in
the eyes of his young guests, it was, nevertheless, a speedily noted
fact that Roque was thawing into more gracious manner.

"I suppose you know that it is only a few hours now until Christmas,
and we must find some special way to observe it."

Billy and Henri could not get the straight line on Roque's remark, but
later realized that the holiday was of the like they had never before
passed.

With a cutting wind from off the icy flow of the mighty river Elbe in
their faces, the boys followed their leader to the docks, where they
boarded a small craft, evidently built for speed, which had steam up
and manned for instant start.

The captain was the same who commanded the deck when the boys had
accompanied Roque on a previous exciting excursion. This official,
standing at attention, stiff as a ramrod, gave no visible mark of
recognition as the passengers boarded the boat, but Billy could have
sworn that he saw something like a twinkle in the captain's right eye
when they passed the gangplank.

"No use asking where we are bound for," lamented Henri.

"Not a bit of use," agreed Billy.

They were out of earshot of Roque, whose tall form, in rusty black, was
outlined in the dawnlight near the wheel of the churning steamer.

The first intimation of what was to be their next landing place came in
the word "Cuxhaven," passed by one sailor to another. The talk was in
rapid German, but Henri caught the drift of the conversation without
difficulty.

"By George," he whispered to his chum, "Cuxhaven is the place mentioned
in Anglin's message."

"You mean Ardelle's message," corrected Billy.

"That's right," chuckled Henri. "I forgot that Anglin had become the
big noise. Yes, it's the very place," he continued, "and it's a great
naval base."

"It's a safe bet that Roque never hits a trail that isn't warm. Take
it from me," and Billy was in great earnest when he said it, "there is
going to be something doing."

Billy's prediction chanced, in this instance, to be more accurate than
are some of the forecasts made by professionals.

It was in a dense fog that Christmas eve when the little steamer ceased
chugging in the wide mouth of the Elbe, and the harbor lights burned
blue. The captain condemned the weather in no uncertain terms, but
Roque seemingly had no care for aught but his thoughts, as he leaned
against the rail, with moody gaze fixed upon the anchored ships and the
dim lines of the city beyond.

As he had shaped, not long ago, the famous raid of the German fleet
upon English seaports, Roque did not underestimate the ability of his
great rival, Ardelle, to open the way for a counter attack. Ardelle was
known by the secret service to be on this very soil--and, surely, for
some big purpose. Minnows were not sent to stir up a pool of this size.

"But they'll find no sleepy towns to blow up here," said Roque to
himself.

He was all for precaution, however, and his intuition was nothing short
of marvelous.

When "Dr. Blitz" and his "sons" went ashore it was the foggiest kind of
a Christmas morning.

A stalwart marine attempted to put the doctor through the question
paces, but the real Roque whispered a fierce something into the ear of
the would-be questioner that set the latter back-tracking in a jiffy.

It was a curious and remarkable fact, but true, that an hour after the
eminent secret agent and his young charges had landed in Cuxhaven,
Billy's prediction, "that wherever Roque is there's something doing,"
was verified. Every submarine cable connecting the fortresses of this
coast sounded alarm, particularly high-keyed the frantic signal from
Helgoland, the fortress island, thirty-nine miles away.

Roque dropped his doctor character like a hot potato when he learned
the import of the flashes. He tossed his traveling case of surgical
instruments into the first open doorway he passed, and the boys were
compelled to run to keep up with his long stride.

Bombs were falling from aloft, exploding among the shipping behind
them, while in front one of the projectiles crashed upon a huge gas
tank.

"The nerve of the devil mapped this out!"

The bitter emphasis of Roque indicated that he laid the blame of this
unexpected invasion upon one head--that of Ardelle.

In the meantime, the fog-ridden atmosphere was riven by blazes of
powder from the shore guns, trained upward, and the air squadron,
Zeppelins and naval seaplanes, were leaping skyward to meet their kind
in aërial battle.

Roque charged madly into the air station, dragging the boys after him.

A seaplane was balanced on the polished ways for the sweeping plunge.

"In the name of the Emperor!" he shouted, shouldering aside the men
holding the poised craft. The same fierce whisper in the ear of the
aviation lieutenant had effect identical with that upon the marine at
the docks.

"Get to your places, you moonfaces"--this stern command hurled at the
boys. Henri bounced into the motor section, Billy settled behind the
rudder wheel, and Roque swung himself into the bow seat.

The long hull was launched with the snap of training, and with motors
humming left the water without a wrench from its skimming start.

The Boy Aviators, certified masters of the air, were at their trade.

They had need of all their skill and daring that day!

"Set your course northwest," loudly ordered Roque. "Hit for Helgoland
like a bolt."

"Look out that you don't hit something on the way!" shouted Henri from
the rear.

The last warning was timely, if Billy had need of warning at all. There
was peril in the foggy stretches.

The upper regions were literally lined with aircraft. No less than
seven naval seaplanes had traveled in advance of the British warship
invasion of the German bay. Having dropped all the bombs they could
through the mist, they were in full return flight to the convoying
vessels. Zeppelins and hostile seaplanes zigzagged on their trail, and
other dirigibles and fighting craft menaced their retreat still further
on.

Billy guided the seaplane he was driving to the higher strata in order
to escape mix-up with the contending airships, but on the thirtieth
mile recorded, Roque, who had constantly demanded distance figures,
ordered a lower flight, and, the fog clearing, the flyers could plainly
see on the waves far below the floating warcraft of the invaders--light
cruisers, destroyers and submarines. The Germans were combating this
array with aircraft and submarines, but so great was Roque's impatience
to reach the fortified island that the motors were put by Henri to the
limit of speed, and so that part of the conflict is not in the record
of the Aëroplane Scouts.

Just off Helgoland, though, the boys had the shock of noting the
crumpling of one of the British seaplanes and the end of a brave airman.

"There's no escape when death stalks you up here," sighed Billy.

"Ware away, boy," called Roque, when the seaplane hovered over
Helgoland, "wait until they see the color of the bottom of the machine
or we will look like a sieve before we light."

Billy "wared away," and with motors at half speed, the seaplane circled
over the supposed most impregnable stronghold in the world, awaiting
some signal of recognition from the fortress.

It was finally given, and Roque directed immediate descent.

On the ground once more, Billy and Henri relapsed into their dutiful
service as "sons" and rear guards of the renowned "Dr. Blitz." The
glazed caps had gone the way of the winds, but, as Billy put it, "we
are still dressed up to beat the band."

The boys noticed that, barring a few skilled workmen and engineers,
they were the only civilians in the streets that evening. They did not
count Roque, for he might turn out to be a general, if occasion served.

The latter had a busy hour with the garrison officers, while the boys
had an idle one, with about as much activity as is allowed a hobbled
horse. It was evident that "Dr. Blitz" held this island as a holy of
holies, secret even to his "sons."

"It beats me," observed Billy, edging away as far as possible from the
guard stationed to keep them out of mischief, "how those Britishers
ever got by this place."

"The bigger question," asserted Henri, "is, if they got by, how in the
world did they ever get back?"

"That's what Roque is evidently trying to find out," intimated Billy.

The boys, while puzzling over the problem of "get by and get back,"
were looking at the huge fortress so tremendously fortified and noting
everywhere an uninterrupted view of the sea.

They also surmised that an alert garrison was ever carefully watching
the waters, day after day, night after night, hour after hour, in order
not to be surprised by the powerful enemy.

"I guess the fog helped some," was the conclusion finally advanced by
Billy.

"And Ardelle somewhere behind the curtain," suggested Henri.

"Oh, go 'way, man; Roque has given you the Ardelle fever."

Billy just then caught sight of Roque bearing down upon them under full
stride.

"Speak of the dickens," he exclaimed, "here he comes now."

The shadows of evening continued to gather, and here and there on the
island lights showed like glowworms. Roque shook hands with his officer
companions. He evidently contemplated leaving in the same impetuous way
that he came, but evidently not by the seaplane route.

A little steam launch tugged at its holding rope, in readiness to dash
away into the misty deep. Two men muffled to the throat waited the
order. Roque, with never a word to the boys, directed them by gestures
to get aboard, quickly following. The launch cut through the now pitchy
darkness of the Helgoland waters. With the island lights no longer
visible, there could only be seen the lantern in front of the little
boat, and it was a dangerous speed to be making, when the helmsman had
scant view of hardly a yard ahead.

But the man at the wheel was in familiar element, to him, and the
scudding vessel never came to drift movement until a glimmering signal
guided to the landing place, the name of which would have meant nothing
to the boys if they had had the care to inquire.

This was Christmas night in the Bight of Helgoland.

CHAPTER III.

A THRILLING MOMENT.

UNDER oak rafters, festooned with dried herbs, and toasting their feet
at the cheery blaze of an open, roaring fire, the boys regained the
Christmas spirit that had been sorely subdued in the previous dismal
hour in the wave-tossed launch.

The house that had thrown open a hospitable door at the bidding of
Roque overlooked the bay, and its solid walls had resisted the storms
of a half-century. Mine host, Spitznagle, had he been dressed for the
part, would have come very near to the Santa Claus idea, and even as he
was, some of the idea hung about him in a radiant circle.

He could not, though, have possibly trimmed a tree in manner more
satisfactory than he decorated the big, square table in the center of
the wooden-walled dining-room, within easy distance of that first-class
fire. Sizzling sausages, small mountains of crullers, fragrant coffee,
mulled cider, and such like in quality and quantity, indicated a royal
spread.

Roque, who had been prowling around somewhere outside for a time,
suddenly preceded a gust of sleety wind into the cozy interior.

The Christmas spirit had apparently conjured up a bit of a kindly
spell for him, as the iron man fitted into the scene with far less
friction than the boys had anticipated, considering the mood of this
driving force during the trying day.

"Snug haven, this, eh?" jovially queried the late arrival, as he spread
a pair of sinewy hands over the inviting fire. "You're spoiling these
youngsters, Spitz," was Roque's side remark to the blooming boniface,
at the moment stirring some savory stew in a glistening copper pot.
Mine Host waved a three-foot spoon in mock protest against the playful
accusation.

"Nothing like that at all, my dear man," he declared in big bass tone.
"I will not spoil but will cure these children of their hunger."

"Draw up, my hearties," urged Roque, setting example by dragging an oak
bench alongside of the bountifully laden table. Billy and Henri jumped
at the bidding.

"Where are the men that brought us over?" asked Billy, presuming upon
the fact that Roque was in one of the rare periods out of his shell.

"Back, I hope, where they came from," briefly replied Roque. "Those
fellows are hardy stock," he added, "and can see in the dark. Don't
worry about them."

"Cuxhaven is some aircraft place, isn't it?" Henri put this wedge in
the conversation.

"Perhaps it is," acknowledged the secret agent, "and" (grimly) "it may
soon return the upper-story visit just paid with a cloudful of warcraft
that will start a general hunt for cover."

"Had you ridden often in airships before to-day, Mr. Roque?" inquired
Billy.

Spitznagle muffled a chuckle by a slight fit of coughing when he heard
the question, and muttered something to himself like "donner vetter!"

Roque turned a quick eye upon the fat offender, and then gave Billy a
smiling look-over before he made response.

"I confess, young man, that I have enjoyed some lofty travel before I
met you, but I am willing to admit that I could not teach you and that
partner of yours many new tricks in flying the heavier than air kind of
machines."

"How about the Zeppelins?" cried Spitznagle, who could no longer
suppress a desire to show his knowledge of Roque's prowess as an airman.

"Hold your peace, Arnold," advised the secret agent, shaking his finger
at the eager champion, "my business compels me to learn a little of
everything, and it's all in a day's work, anyway."

The boys were satisfied that Roque's renown had not all of it been won
on the ground. Spitznagle would have made a good witness to that effect
if he had been permitted to speak.

While the tall clock in the turn of the winding staircase leading to
the upper floor of the old house was whanging the twelve strokes of
midnight, Roque and Spitznagle pledged the fatherland with uplifted
goblets, and Billy and Henri offered a silent toast to the assured soft
beds upstairs.

When the early morning brought no disturbance of their inclination for
a little longer time to press the pillows, the boys sleepily guessed
that Roque, for once, was not in a hurry to dash into new territory.
As the sun kept climbing, and still no summons from below, curiosity
overruled napping, and the young aviators decided to investigate the
cause of this unusual consideration of their comfort.

Halfway down the stairway their ears convinced them that the place
was not deserted, for a spirited conversation in the language of the
country was in progress, accompanied by a clatter of dishes, and the
ever present cooking odor of sausage assailed their noses.

Besides Spitznagle, shrouded to the rib-line with his flowing apron,
were three very short men and an extremely long one. The latter proved
to be no other than the giant Zorn. Roque was nowhere to be seen.

The heavy host noisily hailed the late comers:

"Good morning, sleepyheads, and all this fine food waiting for you,
too."

Zorn gave his best wide-mouthed grin, and then went on talking, in
lower tones, however, to his short companions.

Billy and Henri made a substantial breakfast, and in doing so, hardly
felt the need of the constant urging of the boss cook.

They could not imagine what had become of Roque, and as nobody
volunteered to tell them, they concluded not to ask any questions.

The boys observed that one of the short men, with a large head wholly
out of proportion with his stocky body, commanded much deference from
the rest of the party.

Henri learned from the drift of the conversation that this determined
looking individual was Capt. Groat of Friedrichshaven, the great center
of Zeppelin factories, and while the captain was not in uniform he had
the manner of rank.

Billy was quietly advised by his chum what the talk was about, and
wagered that the two strangers were airmen.

"When these fellows commence to flock together on this coast," he
asserted, "you can figure on what Roque meant when he fixed a comeback
to get even for that flying raid yesterday on Cuxhaven."

The boys had withdrawn to the fireplace, and had an opportunity to
exchange comments and conclusions between themselves.

"I'd like to take a whirl myself in one of those Zeppelins," was the
wish expressed by Henri.

"Our flying education has been sadly neglected in that respect,"
admitted Billy, "but, you know, these dirigibles are among the things
made only in Germany, and we're just over, so to speak."

As the morning wore away, Zorn made some remark to Capt. Groat that had
attracted the latter's attention to the boys lounging at the fireplace.
The captain arose from the table and approached Billy and Henri with
outstretched hand.

"You speak the German?" With the question he bestowed a strenuous grip
upon each of the boys.

Henri nodded, and Billy confessed by blank look that he did not know
the language.

"It is easy, the English," politely assured the captain, "and we will
talk it together."

Billy brightened at this. He was not fond of hearing through an
interpreter.

"I hear you are the great aviators, and for so young it is wonderful."

"Thank you, sir," was Henri's modest acknowledgment.

"It is with the Zeppelin I navigate," advised the captain. "You know it
not?"

"Not much," put in Billy, "though we once dangled on the anchor of one,
and another time I fell with a monoplane right across the back of one
of your dirigibles."

"Yes," remarked Henri, "and if it hadn't been for that, there wouldn't
have been any Billy alive to tell about it."

The captain showed a disposition to continue his talk during the
afternoon with the boys, but a new arrival of evident importance
interrupted. This addition to the party was a much older man than the
rest, wore a military cloak, and his long, gray mustache curled at the
ends in close touch with his ears. As he stood at the end of the big
table, now cleared of its cloth, and rested a hand, enveloped in a
gauntlet, upon the shining surface, everybody in the room saluted. Over
the shoulder of this distinguished guest the boys saw the face of Roque.

As if by signal, further increased by the hasty entrance of three
additional numbers, the attending company ranged by equal division on
each side of the table, and all followed the directing movement of the
man at the head of the board in seating themselves.

Billy and Henri were the only bystanders, for though Spitznagle had not
ventured to flop down upon a bench at the table, he perched himself on
a high stool, completely blocking the door leading into the pantry.

One of the short men who had first appeared with Capt. Groat produced
a capacious wallet, and laid out in orderly array a number of neatly
folded papers which had been contained in the leather.

"This is the navigator detailed to determine air currents, sir,"
explained Roque to the chief figure, at whose right elbow the secret
agent was stationed.

The man in the cloak fixed his gaze on the expert with the notes. The
latter accepted this as permission to speak, and read in precise manner
the results of close observation during a recent aërial expedition of
Zeppelins, escorted by armed German biplanes, in the vicinity of Dover
straits.

Henri's quick ear and thorough knowledge of the Teuton tongue put him
in line of complete understanding of the report, and that it seemed
preliminary to a proposed general raid of aircraft on territory with
which he was well acquainted.

Billy's only satisfaction was in watching his chum's change of
expression as the news sifted through the latter's mind. He could see
that there was "something doing."

So intently interested was the gathering at the table in the reading,
that the very existence of the youthful outsiders seemed to be
forgotten.

"Good; excellent!" commented the chief.

"It's a game with double trumps." Roque held the affair at Cuxhaven as
a choking memory.

"There'll be quite a fall of hot shot, I promise you, if we get started
right." This was the prediction of Captain Groat.

His lieutenants from Friedrichshaven nodded their approval.

In anticipation of a telling counterstroke by their air squadron, the
plan makers at the table puffed up clouds of smoke from pipes and
cigars, freely distributed by the happy Spitznagle when the lengthy
discussion officially ended. In the added hours, when stone mugs were
passing among the thirsty, night had fallen outside, and the benches
were turned to the glowing fire.

While Spitznagle was touching the tips of numerous candles with the
tiny flame from a paper spiral, the empty mugs were being removed by an
oddly dressed fellow, who shuffled around in carpet slippers like he
was tormented with a thousand pangs of rheumatism.

The boys had boosted themselves to good lookout points on the wide
window ledges, behind the lively circle around the fire.

The leather wallet and the survey notes of the expert air traveler lay
separate and apart on the table, just as they had when the reading
concluded.

Billy was idly watching the halting action of the queer servitor, when,
to the great astonishment of the watcher, the apparent cripple, with
rapid hand movement, under cover of the wiping cloth he carried, deftly
lifted and concealed the papers somewhere in the scarecrow garments he
wore.

It was a tense moment. The word that would have turned things upside
down in that room trembled on Billy's lips. But one of those remarkable
instances of mental telegraphy checked the utterance. The man who
had stolen the papers felt that his action had been detected from an
unexpected quarter, and his eyes lifted to the very point of danger.
There was an appeal in the look--and something else, a flash of
recognition that compelled a response. They were the smiling eyes of
Anglin--or, as Roque would have it, Ardelle.

Billy, tongued-tied, saw the bent figure slowly shuffle toward the
kitchen. He inwardly trembled at the thought of the stocky airman
suddenly turning from the fireplace to seek his precious reports. He
added another little shake in advance of the turmoil that was bound
to be raised, anyhow, no matter how soon or how late the loss should
be discovered. But the consolation of delayed discovery would be that
Anglin had a chance to save his neck.

"What's the matter with you, pal?" Henri had just noticed that Billy
was off color and wide-eyed as a trapped rabbit.

Billy, for caution, laid a finger on his lips. "I've seen a ghost," he
whispered.

With a glance of apprehension at the group circling the fireplace,
Billy leaned against the shoulder of his chum and with underbreath
speed told of the presence of Anglin and the taking of the papers.

Henri was thrilled by the exciting story poured into his ear, and
immediately took on his share of anxiety as to the outcome of Anglin's
daring action.

Bursts of laughter resounded at the fireplace. The company was then
applauding some humorous tale volunteered by Zorn, who had risen like
a tower to impress the point of his story.

"Gee," murmured Billy, "will they never quit?"

"Don't fret," advised Henri, "the blow will fall in due time."

It did fall a few minutes later.

The main mover of the meeting was saying: "Gentlemen, it is nearing a
new day, and there is great achievement before us. We go to prepare for
it."

Benches were pushed back to clear the way, and this scraping sound
had hardly ceased when the short airman, who had made the interesting
report, hurried to the table for his valuable records.

The boys leaned forward in breathless suspense.

CHAPTER IV.

THE STOLEN PAPERS.

"MY papers! The report! Has anybody seen them?"

The owner of the wallet shook it vigorously over the table, to
assure himself that he had not replaced the records there, and then
quickstepped the whole length and around the board, lowering his head
again and again beneath the polished surface to see if the documents he
was excitedly seeking could have possibly fallen on the floor.

"What's that?" cried Roque, starting forward. "You've lost the papers,
you say?"

"I didn't lose them," almost shouted the airman, "they were left on the
table, and if they're gone, they've been stolen."

"Hey, my friend," remonstrated Spitznagle, "we have no thieves in this
house, and no enemies to the cause."

"This is no time to bandy words," roared Roque, "shut and bar the
doors"--this last command directed at Zorn. The giant jumped at the
bidding and sent the bolts rattling into their sockets.

The savage energy of Roque ruled all to silence. Even the power under
the cloak refrained from advising.

The secret agent dismissed suspicion as to the active participants in
the conference, and as to the loyalty of Spitznagle he had not the
slightest doubt. The trial horses must needs be two pale-faced boys
backed up against a window-sill.

Roque, with his hands deep in his pockets, a habit he had when stalking
a suspect, walked around the foot of the table and stood directly in
front of the pair, fixing on them that gimlet gaze he used to terrorize.

Billy and Henri, when at bay, were the most keenly alive; their nerve
always served them most in the supreme test.

They faced their inquisitor without an outward tremor; their previous
anxiety was known only to themselves, and now admirably concealed.

Roque realized that he had no fluttering birds in his hands, and also
was aware that a search of their persons was only required to acquit
or convict these youngsters of the actual theft. He knew that they had
not left the room, though why he had not long ago sent them upstairs to
bed was a slip of mind he could not account for. But it had occurred
to Roque that the boys had been in a position to see the table all
the time since the company adjourned to the fire, and whatever had
happened in regard to the papers they, if not the light-fingered chaps
themselves, must have witnessed the perpetration of the steal. So he
changed his tactics.

"Now, boys," he began with insinuating address, "there is a very ugly
situation here, and as I have always heretofore found you dependable,
cannot I now depend upon you to help me clear this up?"

Henri shook his head, in denial for both. "Search us," he said.

Roque, whose remarkable judgment of human nature has before been noted,
felt in an instant that the suggested search would develop nothing.

"Who took the papers then?" he fiercely demanded.

"We were not on guard duty." Billy was inclined to resent this
bullying, and showed it by his answer.

"Strip them," urged the short airman, who thought he, as the loser,
ought to have a word in the controversy.

Roque waved the man away, and then abruptly moved to where Spitznagle
was sitting, a picture of despair.

"Who was in the house to-night besides those now present?" was the
question fired at Mine Host.

"Nobody but Conrad," assured Spitznagle.

"Who the devil is Conrad?" Roque fairly jumped at this information.

"Why, a poor crippled fellow, as queer in the head as he was in the
legs, that I had helping in the kitchen. He lost his job as cook on the
coast line steamer _Druid_ on account of rheumatism, and they sent him
up here to me."

"'They sent him up,' did 'they?' And now when did 'they' send him up?"

"About a week ago. But what's all this about Conrad you're asking,
Roque? I'll have him in, and you can judge if he is worth a moment's
notice in this kind of affair." Spitznagle started for the kitchen
door, Roque at his heels.

"Conrad, Conrad," called Spitznagle.

"Conrad" had flown, leaving nothing behind him but his rheumatism and a
dingy apron.

"Yell till you're hoarse, you fathead," raged Roque, "and the cows will
come home from nowhere before you get an answer."

While Spitznagle was staring into vacancy, Roque stormed back into the
dining-room and announced:

"We've been the dupes of that spy Ardelle. Nobody but he could have
gotten away with a venture like this. But" (gritting his teeth), "I'll
beat him yet. I say, Vollmer" (turning to the aërial recorder now
minus his records), "you have the whole thing in mind and we'll strike
while the iron is hot. We may outride the warning, for he can't get it
flashed from this coast."

The man in the cloak came to the front on this proposition. "The word
is 'immediate,'" he proclaimed.

A speedy departure was in order, and Roque crooked a finger at the
young aviators, bidding them follow.

"You are going to be mighty useful, my flying friends," he said, "and
you'd better be." There was grim emphasis in these last words.

At noon the next day the boys were again tramping around after Roque
in Cuxhaven. The character of "Dr. Blitz" was no longer in the play.
Roque was trimly set up as an aviation lieutenant, and it was really
wonderful how easily he merged into each part he assumed. "Students" no
longer, Billy and Henri were happy in resuming their flying clothes.

"Best becomes our style of beauty," as Billy would have it.

There seemed to be some unforeseen reason for delay, as the aërial
expedition did not start forthwith, as intended. Indeed, it did not
start from Cuxhaven at all. It might have been that Ardelle's theft of
the guide records had put a spoke in the German wheel, but as to that
the boys could only hazard a guess.

It was on the twentieth day after the adventure in the house of
Spitznagle that the young aviators again had the opportunity of
operating a seaplane with Roque as directing passenger, and the
uninterrupted flight brought them to the island of Amesland, for
though Cuxhaven was counted as the airship base, it evidently was the
intent to project the return attack on the English coast from the
out-to-sea point before named.

What an array of the warcraft of the "upper deep"--the great
dirigibles, seaplanes, destroyer, artillery spotter and scout
aëroplanes. The boys were in their element. Even Roque had a smile for
their enthusiasm. It was not the war spirit that animated Billy and
Henri--they reveled in the show as airmen delighted with the life.

In this camp were none but the suicidally brave type of fighters,
and it was only that kind fit to essay the trackless line of three
hundred miles over the sea. From what the boys, or, rather one of them,
Henri, could learn from the camp talk, a pair of the latest Zeppelin
dirigibles were to participate, but the main movers of this attack
were evidently to be airships of the small, non-rigid Parseval build,
for bomb work. The truth of the matter was, the young aviators, at
the order of Roque, were so taken up with the tuning of a seaplane
just before the fleet went aloft that they could not have listed the
starters with any degree of accuracy.

They only knew positively that they were going aloft, and their own
machine would require their individual attention. About 8:30 that night
the glare of a powerful searchlight from one of the German airships
directed its rays over the heart of the English city of Yarmouth. Two
bombs dropped almost simultaneously.

The boys saw the city below suddenly plunged into darkness. Five more
bombs were hurled from the sky. The fleet then swiftly moved northeast,
and more bombs crashed into the town of Kings Lynn. Roque had assumed
no active part as a leader in the deadly maneuvers--his was a thinking
assignment. It was midnight when the fleet turned eastward and fled
back across the North Sea.

"It might have been London," muttered the secret agent, "if the game
could have been played without a break."

Preparations to repel just such an invasion had been made in the great
city.

Ardelle must have gotten his warning across, but the coast towns failed
to heed it.

The Roque machine kept its speed when the balance of the fleet checked
flight at Amesland. The secret agent was bound for Cuxhaven, doubtless
to plan another tiger spring at the foe. He was all for air campaigning
these days.

"You will witness the sight of your lives, you young cyclones, before
last night's mist of the North Sea dries in your hair."

This significant remark on Cuxhaven docks set the boys in the highest
state of expectancy. It was seldom that Roque billed anything ahead of
time, and surely something extraordinary must be in the wind.

Three days later, from a dizzy height, they witnessed a sky battle
without parallel in military annals, and which dimmed the memory of any
of their previous remarkable experiences in the war zone.

The French coast town of Dunkirk, to which the boys had on a happy day
gone by been delivered by submarine and taken away in a seaplane, was
the ground center of this spectacular conquest of the air--the first of
its kind in the history of the world.

Twenty hours earlier a fleet of British seaplanes had bombarded the
Belgian port of Zeebrugge, held by the Germans, news of which had soon
after reached the mystery man, Roque, by way of one of the innumerable
channels of communication with which he kept himself constantly in
touch.

The German bird craft suddenly appeared over Dunkirk like a flock of
gigantic sea gulls.

Explosive missiles fell as fiery hail upon the town. The tocsin sounded
in the high tower of Dunkirk church, and the blue and white flag of the
town was run up.

The roar of the fort guns, firing shrapnel, was heard, and all around
the German fliers white puffs were bursting, as the pilots guided their
machines in low-swooping spirals.

In compliance with the snappy commands of Roque, Billy circled the
seaplane to every point of observation vantage, while the secret agent
viewed the action of the armored Aviatik biplanes, dashing here and
there with the sun glinting on their steel sides.

"Look there!" shouted Henri, rising and clutching a stay to preserve
his balance. The air was clear, and the scene was open even to the
naked eye.

Billy, at the wheel, risked a glance sideways.

A squadron of British aviators, encamped on the outskirts of Dunkirk,
had taken the air to engage the raiders.

One speedy biplane darted straight toward the German craft. Henri saw
the aviator clutch the levers of his machine in one hand and with the
other unsling a rifle, beginning fire at a German birdman below him.

A half dozen armored aëroplanes of the raiding force swarmed in upon
the daring Briton. His machine was peppered with lead, and it was
apparent that the man had been wounded as he dipped toward the earth to
evade the encircling Germans.

Other English aviators swept into the whirling combat, and to the
rescue of their wounded leader. The raiders turned toward the north,
now being shrapnelled by anti-aircraft guns stationed along the coast.

Roque pointed upwards, signalling for rapid ascent, and at six
thousand feet the seaplane, with tremendous burst of speed, soon
overhauled and outdistanced the slower warcraft, making a wide detour
over the sea, thus avoiding the volleys of rifle shots from the Allies'
infantry near Nieuport.

Roque, looking at his watch, turned to Billy, just behind him,
remarking:

"That much in fifty minutes is not often recorded--of these things they
shall sing on the Rhine."

In Bremen the boys paid grateful tribute to rest after the strain and
stress to which they had been put by their relentless taskmaster.

"I feel," said Billy, "like the hump between my shoulders is going to
be permanent, and I couldn't keep my elbows down to save my soul."

"If I could only get the whirr out of my ears, I'd be satisfied," was
Henri's complaint.

It was not long, however, before the boys found relief from the kinks
in their backs, and were ready and eager for the next move in their
adventurous careers.

Just around the corner from their hotel was the very café where they
had the thrill of seeing Anglin's face in the mirror while they were
dining there with Roque.

"Wouldn't it be funny if Anglin were to bob up again while we are here?"

"I think, Billy, that it would be a tragedy if Roque had any inkling of
it."

"Don't you hold the thought for a moment, Henri, that you could catch
the Calais weasel asleep. Oh, I say, there's a concert on downstairs,"
quickly concluded Billy, as the notes of violin and piano were wafted
above. "Let's hunt the music."

A high tenor voice was merging into the accompaniment when the boys
reached the floor below, and they saw that the singer was one of the
curly-lock type, and in evening attire.

What of the eyes, though, that gleamed upon the Aëroplane Scouts as
they stood in the doorway--the artistic make-up could fool them, but
there was no mistaking the smiling orbs under the blackened eyebrows.

Fox tracks were mixing again!

CHAPTER V.

WHEN THE LIGHTS WENT OUT.

THE vocal efforts of this new favorite had called forth round after
round of applause, for good music never went amiss in Teuton territory.

Among the vigorous hand-clappers the boys noted a well-groomed man,
apparently about forty, wearing an affable manner and the best clothes
that the continent can produce.

Henri nudged Billy. "Size up Roque, won't you, please, and isn't he a
dandy?"

Billy was first inclined to doubt the identity of their taskmaster, who
a couple of hours ago was a far cry from being in the glass of fashion.
Never before had the boys seen him in that sort of rig.

"You're dead right, Henri, it is the old scout. He's a corker, sure!"

This note of admiration had scarcely sounded when Roque was joined by a
slender, wiry individual, also set up as a swell, with a shock of sandy
hair, and sporting a monocle.

The fellow with the quizzing glass had apparently moved to get a better
view of the singer, as well as to get in touch with the secret agent.

"Wonder if that's the man who spotted Anglin on the parade ground at
Hamburg?"

"Don't let your imagination run away with you, Henri," advised Billy,
who in speaking was careful not to indicate that his attitude was
anything but careless.

The sandy-haired man was taking the same precaution, but Henri, nursing
the idea that would not down, was more and more impressed with the
belief that the elegant figure was seeking the measure and not the
music of the warbler at the other end of the room.

If the singer had sized up the situation, it had not affected his
rendering a bit of light opera that was just then exciting an encore.
There was nothing at all the matter with his German or with his voice.

Nobody apparently was more delighted than Roque, and he appeared to be
expressing his opinion to the wiry listener beside him.

The latter bowed politely and then sauntered toward the revolving door
leading into the lounging section of the hotel, fingering a cigar as he
proceeded.

Henri edged around nearer to the piano, the player of which was
completing the program with a national air, the melody of many voices
aiding the performance.

Billy had hardly realized the desertion of his chum when he saw that
Roque had changed his position, and was standing nearest the door
leading to the street. The secret agent shifted something from his hip
to the sidepocket of his coat, and Billy caught the glitter of that
something in the swift movement. The boy guessed then that there was
trouble brewing.

In the meantime, Henri, in an innocent sort of way, pushed still closer
to the pianist, who was hitting the high notes in fine style.

As he passed within a foot of the singer, now idly posing, with an
elbow on the piano top, he, without turning his head, joined in the
triumphant chorus, but changed two words at the climax, and "beat it"
reached Anglin's ear.

The French sleuth never moved a muscle, and it was as if the warning
had been passed to a man stone deaf.

Anyone posted, however, would have known that within an arm's length of
Anglin was a wall switch which controlled the electric lights by which
the room was so brilliantly illuminated.

Billy had just had the experience of being rather rudely thrust aside
by a couple of burly troopers, who seemed inspired to get as quickly as
possible into the very center of the select circle.

"Get him!"

As this command rang out the astonished pleasure seekers started a
panic, as if an alarm of fire had sounded. There was a rush for every
doorway, but every way of departure was blocked by stalwart guardsmen.

Billy was not among those who tried to break through the doors--he was
dodging among the charging force sent in by the loud orders to "get
him."

Click! The room was suddenly shrouded in darkness, penetrated a little
distance only by the lights beyond the entrance of the lounging room
section.

The pursuing force, working from several directions, ran into one
another's arms. The pianist, familiar with the place, leaped for the
electric switch, and turned on the flood of light.

Everybody was present but the singer!

Henri had a perch on the keyboard of the piano, which he had sought to
save a mad tramping on his feet.

"Set you to catch a weasel," sneered Roque, as the sandy-haired man
stood staring at the shattered casement of the tall window overlooking
an inner court of the hotel.

"He can't get clear away," retorted the sandy one.

"Stop him then," challenged Roque. "Don't stand there like a stoughton
bottle."

The pursuers scoured the building from bottom to top, and every street
and alley roundabout, but it was a case of looking for a needle in a
haystack.

Roque was in a black mood. Once more baffled by his cunning chief
adversary, the only one he acknowledged in his own class, and on his
own stamping ground--it was a bitter dose for the master craftsman.

Did he remember how he himself had spread a web over Britain, woven so
finely that even Scotland Yard could not see it? Yet he rebelled at the
like cut of a diamond.

"Stir your stumps," was his peremptory address to the boys, and they
trotted to catch his long stride out of the hotel.

The sidewalks on both sides of the street were crowded with curious
onlookers, attracted by the reported doings inside.

Roque bucked the line like a football star, and Billy and Henri
followed in the cleared space without special exertion.

"He doesn't care whom he pushes," observed Billy, as he listened to
angry protests along the line of travel.

Both of the boys were eager to talk over the latest disappearing act of
that wonderful Anglin, but not so anxious as to take chances with Roque
in earshot.

The secret agent turned into a silent side street, and stopped before a
heavily grated door in the gloomy front of a solid stone building that
was a skyscraper in height. Reaching through the grating, he evidently
opened way of communication with the interior, for in a moment or two a
glimmer of light splintered through the barred entrance, the ponderous
lock creaked, and the door swung back on its massive hinges. A skull
cap and a gray beard showed behind the lamp shining in the doorway.
Roque pushed the boys ahead of him, and their closing in was marked by
a clang behind them.

They followed their guide through a long corridor and into a modern
high-power elevator, that shot noiselessly upwards. It was a circular
room into which they stepped, the very tip of a tower, and a wireless
telegraph apparatus was there in operation.

"How is it working?" promptly questioned Roque of an operator who was
off his turn, and relieved of his headgear.

The man jumped to his feet, all attention, and replied: "There's been
hardly a break for an hour, sir."

Here was one of the hidden intelligence stations that accounted in
part for Roque's ability to get searching and quick information. That
he should initiate the boys into his particular secret service methods
indicated a determination that they should never get away from him.

As Billy said to Henri at a chance moment, "He thinks we are booked
for a life job as his air chauffeurs."

They were not aware as yet that in the extensive grounds, housed at the
water's edge, was the seaplane in which they had recently traveled so
far, and in addition a big biplane and two monoplanes were in hangars
ready for service. Also the most speedy of steam launches rested at the
private wharf.

Roque was a recognized genius, like every cog in the German wheel,
absolutely thorough in his methods, and the means placed at his
disposal were practically limitless.

Billy and Henri had climbed into the steep embrasure of a tower window
and were enjoying the magnificent view spread out before them.

"How about my imagination now?" Henri was recalling exciting incidents
in the hotel. "Didn't I get the figure of the sandy man as a spotter?"

"I think you did," admitted Billy. "But," he continued, "I didn't take
much stock in the idea until I saw the revolver in Roque's hand. Then I
knew that the fat was in the fire."

"I gave Anglin the cue to beat it, and I did the trick by breaking into
that Rhine song," exclaimed Henri. "Yet he never made a move until the
yell of 'get him,' and I thought the jig was up, sure. He's the coolest
hand in the business, that fellow."

"Some of these days, maybe, he'll fall a little short in one of those
getaways, and that will mean a tumble into six feet of earth."

"Not he," stoutly maintained Henri, "he's the regular man with a
charmed life. Say, I can't help laughing even now when I think of
Spitznagle calling 'Conrad,' and the expression on Roque's face."

Billy gave Henri a kick on the foot. Roque was approaching with a sheaf
of telegraph messages in his hand.

"What are you boys jabbering about? I want you to go down to the wharf
with Albert and get the seaplane in trim. I'll join you in half an
hour."

Albert, a strapping youth, with the breezy way of a sailor, guided the
boys across the grounds to the hangar, and watched with interest the
making ready of the airship.

"That's not my kind of a boat," he briskly stated, "but I'll be bound
if this kind of craft didn't give us submarine workers a Christmas
surprise. Ever travel in a submarine?"

"We had a ride in one that we will never forget," replied Henri, as he
applied the oil can to the big motors.

Billy, busy with the steering gear, was not expected to answer, as he
did not understand the question.

"It is all a question of ups and downs, anyhow," went on Albert, "bombs
from above and torpedoes from below."

This trade discussion ended with the arrival of Roque, who had severed
himself from style and was again in aviation attire.

"Now, my carrier pigeons, you are in for a homing flight, that is,
Hamburg; and it may be some time before you again get a breath of this
port."

With this assurance the seaplane was launched and took the airline for
Hamburg, leaving Albert to his own devices.

The travelers soon had sight of Zorn's ever-ready grin at the home of
"the well-known tradesman."

"We've been through a lot since we were last hauled out of these
feathers," remarked Billy, as he bounced into the bed pillows that
night.

Happily, "coming events do not cast shadows" for sound sleepers.

Roque had departed for the city before the boys charged into the
breakfast room.

"He has gone to the store," announced Zorn, who uncovered his teeth an
extra inch, in compliment to his own humor.

"Let's go over to see Lieutenant Hume," proposed Billy, after breakfast.

"Just the ticket," agreed Henri, "I'm crazy to get a peep at the old
flying quarters again."

But Zorn objected to any move that Roque had not ordered.

The boys had to be satisfied with the prospect, for to run against
Zorn would be akin to tackling a mountain.

When Roque returned, sure enough, he was again playing the
merchant--horn, spectacles, and all.

"Ah, young sirs, kindly waiting for the weary worker?"

"Same old blarney," muttered Billy.

Zorn chuckled as he relieved the "merchant" of his hat and overcoat.

"Some time ago I believe I told you that here you were only balancing
on the edge of the great empire, and there might be an opportunity for
you to see much more of the country. The opportunity is at hand. I have
been called by trade interests further afield, and as I cannot consent
to a separation, you will continue as my companions."

In his hour of relaxation, Roque really enjoyed this sort of word play,
and he eyed the boys to see if they appreciated the fact that all of
the best actors were not on the stage.

He was sure of Zorn's sincere appreciation. This man had seen the chief
in many parts.

Henri accepted the cue, and, with a profound bow, and a hand on his
heart, replied in kind:

"My dear Herr Roque, we would grieve if you left us behind."

"What of you?" Roque turned to Billy.

"Oh, anything goes with me." The boy from Bangor always hit straight
from the bat.

The last evening of many in Hamburg was a very pleasant one to the
boys. Roque's intimate knowledge of London and Paris was displayed
in entertaining way, with no reference to his own exploits as the
cleverest conspirator that ever invaded court and palace. He expressed
regret that he had never seen America, and induced Billy to tell about
Boston and Bangor.

It may also be recorded that with this evening the boys unconsciously
said good-by to the character of the Hamburg merchant. They went far
with the many-sided man, but never again saw him in the rôle imposed by
this big city on the Elbe.

When the boys retired they left master and man--Roque and
Zorn--conversing before the fire. With the coming of the morning, the
journey to the unknown began, and the Aëroplane Scouts had no idea of
its purpose or their assignment in the new sphere of action.

That it would, however, include further conquest of the air they might
have guessed.

CHAPTER VI.

A FLYING VICTORY.

IT was a great day for the boys when they set foot in imperial Berlin,
with its palaces, art galleries, museums, parliament building,
monuments, magnificent parks, and over all its martial spirit.

Roque, by which name, it might be mentioned, he was not known in this
heart of the empire, soon demonstrated to his charges that he was the
man higher up by his manner of getting about, and the high cost of
living had no worries for him.

"Who'd have thought that we would be hitched up to a ten-time winner
like this?" Billy was content for the time being to be allied with
power.

Among the many who answered the summons of Roque in the intelligence
bureau, the young aviators were most interested in a score of blond,
blue-eyed, well-set-up Saxons, renowned as Zeppelin navigators, who
were destined to guide the "terrors of the air" in furtherance of
another raiding plan taking form in the fertile brain of the eminent
promoter of trouble for the enemy.

While the boys had faith only in the heavier-than-air machines, they
conceded that the risk taken by the Zeppelin crews entitled the latter
to brush elbows with the crack flyers of the other kind of bird craft.
It was also true that when a Zeppelin got anywhere it was a tremendous
factor in war. And it was no question but that the Fatherland had gone
Zeppelin mad.

Woe betide the hostile airmen who dropped the bomb on the Zeppelin
works at Friedrichshaven if Roque had the means of catching them. It
was only another score that he had marked up against Ardelle, whom
the master agent of the empire charged with planning this destructive
performance.

"Roque said he was going to show us where these gas cruisers grow,"
Henri advised Billy one evening, getting this news while his chum was
engaged in an argument with a Zeppelin worker.

"Something I've been wanting to see," exclaimed Billy. "I owe something
to a Zeppelin, even if it is like a balloon."

This last was a sort of side swipe at the man who had been on the other
side of the argument.

"There is one thing sure, these dirigibles can't camp out." This was
Billy's first remark in Friedrichshaven.

He was peering into a big steel-framed shed with a glass roof which
housed one of these grim engines of the air--a great cylinder flanked
by platforms. This newest of the huge airships was about the length of
a first-class battleship, and the opinion of the young aviator that it
could not drop anywhere and everywhere like the aëroplanes he drove was
not a prejudiced one.

When Henri had a look at the powerful motors he was impressed with
their capacity to drink up petrol at a most appalling rate.

"What's her top speed?" he asked one of the big fellows who had
traveled over from Berlin with them.

"Forty-five miles in the calm," was the reply.

"Gee!" exclaimed Billy. "We could get a seaplane home for breakfast
while they were waiting supper on you!"

"Yet," claimed the Zeppelin expert, "it's the car they're all afraid
of."

"It certainly does look like a scaremark," admitted Henri, who
remembered a certain evening on the Belgian coast, when he was one of
the company aboard a stranded hydroplane dragged ashore by the swinging
anchor of a Zeppelin, which loomed overhead like a cloud, and buzzed
like a million bees.

A gang of at least a hundred men swarmed about the shed when the order
issued for a trial trip of the new super-Zeppelin, a sample of the
fleet in course of building, and Roque carefully noted every detail of
equipment.

The gas chambers were fed with pure hydrogen, no common coal gas,
and many thousand cubic meters were in the flow of this one envelope
filling.

"Guess they'd have to carry a hydrogen factory around with this outfit
to keep it going," observed Billy, as he noted the elaborate process.

"Not that bad," advised the man at his elbow, "this gas can be
transported from the factory in cylinders under pressure."

"Just think of it," put in Henri, "I heard them say just now that it
took thirty gallons of petrol an hour to buzz these motors."

"Biggest thing I know in the air business. I wish Captain Johnson could
see an expense bill like this. He'd have a fit." Billy would, indeed,
have counted it a red-letter occasion if his old friend, and the boss
airman of Dover, were really at hand to take in this show.

To go aloft in an airship about which they were not thoroughly posted
was a brand-new experience for the boys, but they were not in the least
degree like the proverbial cat in a strange garret. It was easy riding,
and none of the guns pointed their way. Billy carried a memorandum of
a British military biplane, with a record of 10,000 miles, which Henri
and himself had once patched up, that had been hit by 250 rifle bullets
and sixty fragments of shells. He wondered if the immense craft in
which they were sailing could have floated with, proportionately, about
ten times that amount of lead poured into her. But Billy, of course,
did not then know much about Zeppelins.

Roque, however, was eminently well satisfied, particularly with the
improved method of distributing explosives where they would do the most
harm. The airship had a special armored compartment for bombs near the
propellers and a big gun mounted in front to destroy aëroplanes. "Get a
fleet of these over the English channel," he proclaimed, "and somebody
would think that hell had been moved upstairs!"

"I'll say this much," announced Billy, "I'd take an ocean voyage for my
health if I knew when they were coming."

"But if the fighting crowd over there had the date and the hour, I'll
promise you that the reception your fleet would receive would be warm
enough to boil an egg." This was Henri's prediction.

"We never advertise," grimly remarked Roque.

When the Zeppelin had completed her trial trip and had again been
housed by the small army of workmen, Roque informed the boys that he
was going to give them the chance on the morrow to show their mettle in
a biplane test, which was to decide the relative merits as to the speed
of two special designs.

"I am going to put you up to jockey the machine that I favor," he said,
"and, mind you, the aviators that will drive against you are among the
finest in our flying corps. I always pick my men by personally knowing
what they can do in any line of action. They seldom fail me, and it is
with you to make good."

"We're going some, Herr Roque, when we come up to your standard,"
replied Henri.

"See that you are 'going some' at the finish of the race to-morrow,"
laughed Roque.

"It will be because something breaks if we don't hit the high mark,"
assured Billy.

"Go over and size up your winged steed," directed Roque, pointing
to a hangar across the field. "Show them No. 3"--this to one of the
attendants.

"This is no mosquito," announced Billy, after a view of the fine lines
of "No. 3."

"Speed there, I tell you, old boy," was Henri's comment as he walked
around the rigging, "and carrying armor, too."

In an hour the boys had fully comprehended all the new features of this
up-to-the-minute machine. They had been builders themselves and knew a
good stroke of the business when they saw it.

Returning across the field, Billy and Henri were introduced to the
rival aviators by Roque. The German airmen were a jolly pair, and
showed by the professional courtesy they exhibited to the two of their
kind that the coming contest was wholly a friendly one, and the results
to be of value to the flying corps.

"No. 2 is a little older than your machine," was the greeting of one of
the Teuton experts, "but it can hold its own."

Roque, speaking for his champions, gaily disposed of this claim:

"Keep your eyes open to-morrow, Fritz, or you will get lost somewhere
in the rear."

"No fear, sir; there are no cobwebs on No. 2."

"What are they talking about, Buddy?" asked Billy.

"They just think they are going to beat us, that's all," interpreted
Henri.

A bright clear morning presented itself for the aërial race, and Lake
Constance lay like a broad mirror under the sunlight. The course was
set due north and straightaway for twenty miles, and the turn fixed at
a high point called Round Top, upon which, Roque informed the boys, a
tall flagstaff had been mounted.

There were no preliminary trials, for both machines had been carefully
groomed, and each was as fit as a fiddle.

With the aviators up the biplanes scudded down the field for the rise,
and got away upon almost equal terms, the German drivers slightly in
the lead, through better acquaintance with the lay of the ground. They
trailed a yellow streamer, while the boys floated a band of black.

The ascent reached 2,000 feet, when the machines darted north like
arrows. Roque and a group of officers about him followed the speeders
through field glasses.

"They would run a swallow to death," remarked the secret agent to the
aviation lieutenant at his side.

The aëroplanes had dwindled in the vision to mere specks, and there was
no telling which was in the fore.

"Ah, they are headed back!" cried Roque. "Now for the show-down."

The glasses revealed the specks moving twin-like, and such was the
terrific onrush that the crowd surging in the field soon caught a view
of the contestants in growing size.

One enthusiast shouted: "Fritz will shut them out!"

But the glasses did not uphold the prediction. The machine with the
black streamer was evidently using the reserve power that had been
claimed for the newer make, and Henri was getting the best out of it.
Yet the first-born craft was being handled in a masterly manner, had
plenty of go to spare, and five miles still rolled between the speeders
and the finish flag.

Now four, and the machines were bow and bow; now three, and the yellow
band flapped a few feet behind the black; now two, now within the mile,
and the whirring of the motors audible to the nerve-strained watchers
below--then the close finish--and the white-faced pilot crowned victor
was Billy Barry of Bangor, U. S. A.!

When the aëroplanes made landing, Roque pushed through the crowd and
favored the Aëroplane Scouts with a forcible slap between the shoulders.

The victors were quick enough to extend hands to the vanquished.

"My friend," cried Billy, giving Fritz a warm grip, "it was only fifty
feet, and it was the new motors that did it."

Then the crowd cheered, while the efficiency committee agreed with
Roque that "No. 3" was the machine to be many times duplicated.

"That was something over a mile a minute coming back, I guess," figured
Billy.

"The fastest heavy craft I ever sailed in," was Henri's expressed
belief.

"I think you youngsters could make a living here if I were to bounce
you," said Roque, who had been talking to some of the factory chiefs.
"But you are hooked to my train for a while yet. And that reminds me
that the mentioned train starts in the direction of Austria in the next
two hours. Vienna is not a slow place, you will find."

As Roque was likely to jump anywhere at the drop of a hat, the boys in
his company had long since lost the emotion of surprise.

Perpetual motion had become a habit with them.

In the Austrian capital the travelers encountered many invalids from
the front, men who limped a little, had an arm in a sling, or a
bandaged head. The Viennese on the surface did not seem to be greatly
impressed by the tragedy of the war--evidently becoming used to it--yet
the determination to fight to the finish, while not as grim as in
Berlin, was there, nevertheless.

Another thing that impressed the boys was that here foreign terms were
still much in evidence--French and English. In Berlin it was different.

As Billy said, "we're in a better mixing town." He and Henri were
told that quite a number of medical and art students from America had
decided that Vienna was safe enough for them, but Roque kept his airmen
close under his wing, and they had no opportunity to pass even the time
of day with any of the U. S. A. crowd.

They had no present desire, however, to attempt a bolt from Roque and
did not believe, anyway, that their detention was just then seriously
affecting their health.

"Time enough to run," was Billy's philosophy, "when his nobs begins to
kick in our ribs."

They were seeing plenty to keep them interested, the arrival of
sleeping-car trains bringing the wounded to the capital, the movement
of troops bound for the Polish or Galician front, the daily sights of
the Ring and the Kartnerstrasse.

Roque, as usual, was up to his eyes in war business, ever behind the
scenes but ever moving, for there is close military coöperation between
Germany and Austria-Hungary. All interests related to the war have been
pooled--one empire gives to the other what can be spared. The king-pin
of secret agents from Berlin served a purpose wherever he went.

He sat in no open councils, but privately conducted many of his own,
was constantly receiving and dispatching messages, and the devices he
originated to aid his disguised subordinates burrowing for information
in hostile territory were too numerous for detail. These latter
operations were not accompanied by band music, for officially this live
wire had no identity.

"If that man took a pot shot at the ocean you would never know in what
direction he was aiming unless you happened to see the splash." Billy
was not far from being right in the summing up of Roque's methods.

Within the next hour the boys "happened to see the splash."

A uniformed messenger handed Roque a telegram. The secret agent hastily
read it, and sprang to his feet, his eyes aglow with triumphant
satisfaction.

"I've got Mr. Ardelle in a stone box at last!"

CHAPTER VII.

THE RAIN OF BOMBS.

THE boys in silence watched the secret agent as he further displayed
his gratification over the news conveyed in the telegram by snapping
his fingers and slapping his knees, completing the performance by
vigorous puffing of a big black cigar, of which brand he always carried
a plentiful supply.

Billy and Henri were just aching to learn more about the reported
capture of Anglin (Ardelle), just where the "stone box" that held him
was located, and how the "smiling sleuth" had happened to run into a
net that he could not break through.

But they were well aware that it would not be a bit of use to seek
the eagerly desired information in advance of Roque's disposition to
give it, and they did not dare openly to show personal interest in the
matter.

It was not until the master plotter had burned his cigar to inch
measure that he thought to address the lads, fixing expectant gaze upon
him.

"They jugged the fox in Alsace, on the way to his home den, and filled
up, I suppose, with some choice morsels to regale the enemy."

"Maybe it's another case of 'now you see him and now you don't.'" It
was Henri who plucked up courage to say this.

"Not this time," insisted Roque. "He is tightly in the toils, and never
a chance to show his cunning. His course is run."

It soon became evident that the speaker proposed to be "in at the
death," as fox chasers call the finish.

In less than two hours Vienna, the city gay and unafraid, was behind
the three travelers, and their next goal the imperial territory of
Alsace-Lorraine.

Into Lower-Alsace, on the last leg of the journey, Roque and the boys
took to horse, with cavalry escort. They were again on real fighting
ground.

Henri picked out of a conversation between Roque and the captain of
the troop the words "Homberg castle," later that a group of important
German officers resided there, and still later that within those walls
Anglin was a prisoner.

Billy was immediately posted by his chum as to the situation.

Upon arrival at the castle, Roque, in that mysterious but effective way
of his, established his footing as a privileged guest, and his first
move was to pass the guard at the door of the strong-room, where his
chief rival in the art peculiar was confined.

The boys without reprimand were close at the heels of the German agent.

Anglin was sitting on a bench, under the checkered light of a high,
barred window. While his face showed harsh lines of great strain, the
inevitable smile was in his eyes. He arose instantly from the bench,
and bowed gracefully to the foe who confronted him.

"Monsieur, you are welcome." This to Roque. Upon the boys he bestowed
not the slightest recognition.

Roque, not to be outgeneraled as a diplomat, inclined his head in
return.

"I came a long way to visit you, sir," he politely stated, "and would
have regretted had you felt otherwise than you have intimated."

This fencing with buttons on the foils was soon succeeded by the sharp
points unprotected.

"Ardelle, the longer the breath is in you the more you can tell; is the
breath worth the telling?"

"You speak in riddles, Monsieur," quietly replied the prisoner.

"Do you deny that you are Ardelle?" demanded Roque.

"Am I now on trial?" was the counter-question.

Roque extended a menacing finger. "Have a care, man!" he thundered.

The prisoner calmly ignored the growing wrath of his arch-enemy,
shrugged his shoulders, and with a wave of the hand indicated that
continued argument was useless.

"You will have until to-morrow morning to decide whether you will
accept me as an advocate or an accuser."

The Frenchman turned wearily toward the window, and with his hands
folded behind him stood watching through the bars the little gray
cloudlets pushing their way through the blue expanse of the sky. It
might be that this view would not concern him after the morrow. He was
thus engaged when Roque stamped his way out of the room. Henri would
have paused in the hope of one look from Anglin but the latter seemed
wholly unconscious of the presence of the lads.

Under the steely exterior of Roque, the milk of human kindness had not
wholly curdled, for he sadly said, half to himself and half to his boy
companions:

"He must expect no more than I could expect; when we fail we fail
alone, and so alone must we suffer."

It was about two o'clock in the morning of the day when Anglin, or
Ardelle, was expected to read his fate in the eyes of those assembled
as a military tribunal. The identity of the prisoner was, no doubt,
fully established, for the boys had noted the presence in the assembly
hall earlier in the night of the sandy-topped man who had started the
hue and cry in the Bremen hotel, where the French sleuth was posing as
a public singer.

Billy and Henri were tossing in uneasy slumber. The only sounds inside
the castle were occasional snores from adjoining apartments and from
the outside the whinnying and stamping of the cavalry horses.

Suddenly the quiet was shattered as if by a thunderbolt. The boys
literally tumbled out of bed, gasping from the shock. A blinding flash
at the windows and another crash.

Soul-shaking cries of "fire!" resounded throughout the building, and
through the halls swept volumes of smoke.

The celebrated ancient furniture in the castle, it having been the
summer residence of French nobility, was fine food for flames, and the
red destroyer soon raged in conflagration.

Crash after crash, and with each concussion myriad sparks shot through
great holes in the castle roof.

Bombs were being dropped from aloft.

The boys hastened with other occupants of the upper floors to the broad
staircase in front of the structure. There they paused, elbowed against
the wall by those pressing from the rear. There was no wild confusion
or panic behind them, however, such as might have ensued under the same
terrifying circumstances with other than trained soldiers involved.
When Billy and Henri took to the wall at the head of the staircase
it was a voluntary act on their part. The same thought with both had
impelled the pause:

Had Anglin been released from the fiery vortex or still restrained by
iron bolts and bars?

The room in which the captive was held faced a gallery running at right
angles from the main stairway.

Pulling their jackets up and over their heads, the boys plunged through
the wall of smoke on mission of rescue--a mission without result, for
the door of the place of confinement was wide open, and no one was
there.

The rescuing party of two then turned their intent upon themselves,
and none too quickly, for they had hardly won safety when the castle
enclosure was wholly enveloped by consuming flame.

Farm buildings adjoining were also ablaze, and the wide highway
stretching away to the east showed whitely in the glare.

In the red canopy overhead winged shadows whirred and whirled, dipped
and leaped.

Billy and Henri proceeded down the road to escape the growing heat and
rolling smoke. When the roaring of the fire had somewhat lessened in
their hearing, they detected a familiar hum, just ahead and closing
down beyond the border of the rising mist of the morning.

As aviators, the boys were instantly aware that an aëroplane was
working near and the proof was immediately furnished by the appearance
of the aircraft itself, swooping into the circle of illumination,
skimming close to the surface of the highway.

The lads sprang forward to greet the aërial visitor, and as they did so
a tall figure, hatless and coatless, leaped from the cover of a ditch
nearby, ran like a deer alongside the skimming biplane, and vaulted
into the frame behind the daring navigator.

As the machine took the uplift, Billy and Henri were so close, and the
fire-flow so vivid, that they plainly saw the faces of both the saver
and the saved.

The man who had jumped into the machine was Anglin; the aviator was
Gilbert Le Fane, the noted airman of Rouen, whom our boys had once
followed in flight from Havre to Paris.

From the fire zone there was coming a hurrying body of men, and rifles
began to spit lead at the swiftly rising aircraft. Too late, though,
to reach the height attained by the biplane. A shrill yell of defiance
floated back on the breeze of the morning, and deep and heavy were the
expressions of baffled rage by those grouped in the road below.

Roque and the sandy-haired assistant could be heard above all the rest.

The boys were again in the rôle of innocent bystanders.

When the sun later replaced the flames in lighting up the sky, not a
trace of the French airmen could be sighted, save the marks of their
raid--the blackened ruin of the castle and smouldering remains of the
adjoining buildings.

Investigation instituted by Roque related solely to the escape of the
prisoner. To put a quietus on his rival had drawn him from afar, and
here again the elusive Frenchman had been jerked out of his clutches,
this time into the very sky.

With the fall of the first bomb the single night guard over the captive
had drawn the bolts that he might be ready to quit his post upon first
order with the Frenchman in close custody. The second bomb so stunned
the guard that he knew no more until regaining consciousness in the
rear courtyard outside. He could only account for his presence there
by the belief that the man over whom he had held watch had picked him
up and carried him out of danger. There was a back way that could be
traveled, smoke hidden, without observation.

"But how about the aëroplanes dipping just at the right time and place
to carry him off?"

This was the point that especially puzzled Roque.

A farmer boy, listening, open-mouthed, to the questioning, offered a
solution.

"You see, Monsieur," he bashfully explained, "it was a ghostly noise
that was making between the big noises, like the wind blowing through
the neck of a bottle stuck in a knot hole. I heard it in the road, a
long way."

It occurred to the boys that this distress signal must have been given
before they got away from the roar of the fire, or while they were
probing the smoke in the gallery to reach Anglin.

"They were flying mighty close down and could probably hear a howl
like that, if they were listening for it and knew what it meant." This
opinion was advanced by Billy.

"I don't much believe they could hear a call from the ground, unless it
came from the business end of a gun." Henri was the doubter.

"It is no use to argue," said Roque. "The fact remains that the air
fellow had his bearings, and he got the lead from somewhere. I am not
giving him credit for being a mind reader."

"That reminds me, Mr. Roque," remarked Billy, "that we might test this
bearing business by a little air trip somewhere and soon."

"I have just such a thing in thought," grimly advised Roque, "and I
will warrant that you will hear a few ground sounds before the quitting
minute. We are going to take a down look at Belfort."

Now Belfort is a French fortress, where the soldiers in red and blue
had been finding security every time they were rolled back from the
plains of upper Alsace.

A tremendous amount of gunpowder had been burned on the flat ground
in front of this stronghold, and our boys were in for a smell of
it--something that would recall perilous travel with Colonel Bainbridge
and Sergeant Scott in previous campaigns.

A wire to Friedrichshaven had started on the way the makes of biplanes
that Billy called "Roque's best bet" since the day of the famous race
over Lake Constance.

"Business will soon be looking up," joked Henri, when he heard of the
order for the shipment of "No. 3's."

The presence of Ardelle in this region, extreme southwestern
Germany, had raised suspicion in the mind of Roque that some special
demonstration was brewing, and the lurid performance of the French
airmen in blowing the roof from over his head served to further elevate
the confirmed idea that trouble and the French agent always traveled
together.

Roque was not here to mix in the actual military operations--that was
not his business, but he was ever open-eyed on the trail of the boss
gamester on the other side. He had expected this time to put his rival
on the safe side of the ground, but spades did not prove to be trumps.

Somewhere in the gap of Belfort, as the valley south of the Vosges
mountains is popularly known, Ardelle was, no doubt, preparing for
another comeback, and Roque was scheming to meet him halfway.

There was no chance to get under the guns of the frowning fortress
beyond the frontier, so the only way to size up the situation was to go
over them.

Here was where flying experts jumped to the front.

CHAPTER VIII.

ALONG THE BATTLE LINE.

WITH the arrival of the biplanes from the factory, the Boy Aviators
were kept busy with brief test flights over valley and plain, awaiting
the convenience of Roque for the wider sweep he was planning. It
developed that the boys were expected to navigate separately on this
occasion, Billy to pilot Roque himself, and Henri to be accompanied
by one Renos, who had been awarded a service badge of honor for his
work as an aërial observer in giving first warning of the advance of a
French division against Burnhaupt, which saved the day for the Germans.

"The seaplane is the rig for weight carrying," exclaimed Roque, in
accounting for this assignment, "but these machines, as you know, are
solely in the speed class, and it is many chances to one that we will
be compelled to tax every ounce of power before we get through. So we
have no use for deadwood."

Renos, who was to sit behind Henri, was the silent man of the
expedition, as far as talking was concerned, but when it came to be
up and doing he could be counted on to the limit. He was a human
route-box of the Sundgau, the fighting territory, and very much at home
in a flying machine. When the two machines one morning flew over the
German frontier, in compliance with the "ready" order of Roque, Renos'
knees were crossed by a wicked-looking rifle, and of the party he was
the only one armed.

Billy, observing this war-like figure, asked Roque if he expected to
get into close quarters on this trip.

"Not unless some of the bomb-throwing crowd that scarred the landscape
the other night should cross our path," replied the secret agent.

As Renos was the qualified guide, the biplane bearing him went to the
front, and Henri received overshoulder directions as to the course to
be maintained.

The apparent reason why the German expert did not pilot the craft
himself was that he wanted a loose hand in case of emergency, and a
free eye for the panorama below. He was satisfied, too, that one as
good as the best was doing the steering.

Henri was instructed to keep a respectful distance from the near
mountain peaks, where the French had mounted artillery, for one round
from these guns, close enough, would have ended the flight and the
flyers there and then.

But Roque and Renos kept constant vigil with glasses, and Billy
wondered that the pair did not get a crick in the neck with all the
head-turning they did.

A sharp order advised the pilots to send the biplanes farther aloft,
and circle. The French fortress of Belfort could be seen directly
underneath.

The aviators well knew that an explosion close to an aëroplane is often
sufficient, through the force of the air concussion alone, to bring
it down, and they knew they could not chance a close shot from the
long-range guns in the fort.

Though the machines now evoluted at greater height, the powerful
glasses enabled the observers to plainly distinguish the movements
below.

It was quickly manifested that the garrison lookout had become aware of
the aërial visitation, and that they did not approve of the color of
the hovering aircraft.

A couple of smokeballs ascended and burst in the center of a cloudrack
far to the right of the machine. Renos broke his record for silence
with a shrill cackle.

"Save your powder, you numbskulls," he shouted for his own satisfaction.

Roque seemed oblivious of the gunplay below. As the biplane described
great circles over the fort, he kept his glasses steadily aimed at a
point in the enclosure over which the flag was floating.

The men who emerged from the officers' quarters all wore the French
uniform.

Roque had evidently cleared up a disturbing point in his mind as he
muttered something about a "fool story," and "I might have known there
was nothing to it."

Having satisfied himself that it was still an independent little war at
this remote point from the main field of operations, and that he had
been misled by some advices previously received, the chief observer
passed the word to his pilot to back-track, at the same time giving
signal to the companion biplane.

As the machines swung around for the return flight, and drew closer
together, Renos gave a megaphone yell through a hollow formed by his
hands:

"Speed for your lives, they're on the wing!"

Above the gentle slopes on the west, leading to the summit of the
mountain ranges, aircraft had arisen, looking, at a distance, like
black dragonflies.

At the same moment, the invading biplanes also had a reminder to hurry
from the fortress they were leaving behind.

A shell burst seemingly quite close to the machine Henri was driving,
and the craft dipped far to one side.

Billy's heart beat up to his throat when he saw the break in the
flight.

But his was an exulting cry when the momentarily stricken flyer
righted, and bored ahead.

"Glory be!" hoarsely rejoiced the boy from Bangor, when his chum again
drew to the upper level.

Seventy miles an hour was the clip of the fleeing biplanes, and no less
speedy the onrush of the aircraft from the slopes.

"Steady, and a little to the right," Renos instructed Henri.

The observer was resting the rifle barrel on the rigging, awaiting a
broadside target.

Sping! One of the attacking aviators was first with his rifle, and the
bullet nicked the armored side of the German craft. Sput! Henri heard
an angry exclamation behind him, and shifted an eye long enough to see
that Renos was nursing a bloody wrist on his knee.

"How hard are you hit?" was the anxious question of the young pilot.

"Nothing to kill," replied the observer, as he used his uninjured
fingers and his teeth in knotting a handkerchief above the wound so as
to compress the severed artery.

With the utmost calm he then deliberately used his left hand in rifle
aiming, and sent a bullet into the nearest hostile machine.

Whether the shot crippled the pilot of the leading pursuer, or whether
it was the menace of the heavy howitzers on the German frontier, which
was now of short approach--the French flyers suddenly ceased to be
aggressive, and with a parting salute of rifle practice, turned back
toward their mountain station, while the German machines dashed across
the line of safety.

Upon landing Billy indulged in a sort of war dance around his chum.

"Thought you were gone that time, sure, Buddy," he cried, "and it was
simply great the way you pulled out of the hole."

"I guess I was stunned for a minute, as though somebody had hit me with
a hammer," explained Henri, "but when I found the controls were still
working, it was a bracer, I tell you. And if there isn't a cool head"
(nodding toward Renos, who was inspecting his wounded wrist) "I never
saw one. He stretched his arms over me ready to take hold if I failed
to rally, and did it as a matter of course. Not a tremble about him,
either."

"What do you think of the No. 3's now, boys?" queried Roque, when he
had dispatched Renos in search of a surgeon.

"They're dandies, all right," promptly agreed the happy pilots.

"They will do to hunt trouble with, anyhow," laughed the secret agent,
who was immensely pleased with the flying achievements of the day.

Roque, pluming himself with the idea that, though he did not hold
Ardelle when he had that artful dodger under his thumb, he had at
least chased his rival out of the empire; and, having also eased his
mind as to the report of a new element in the Alsace campaign, he was
impatient in his preparation for departure. Master of detail though he
was, the big moves only appealed to him.

A great battle was raging at Soissons, on the Aisne river, in France,
and Roque had in mind an aërial journey north, and quick flight across
the border to the scene of the fierce artillery duel, following the
line of march of the mighty force under General von Kluck.

The crippled Renos was replaced in the observer's perch by an aviator
known as Schneider, a very daredevil, and who was at first inclined
to doubt that the boy with whom he was paired had sufficient skill
and courage to pilot a military biplane in an active war zone. Henri
very quickly convinced the doubter that he was very much older than he
looked when it came to the fine points of aëroplaning, and, too, that
when there was an emergency demand for "sand" the youngster had plenty
to spare. Schneider had additional assurance of capacity when he was
advised that both of the lads carried Roque's indorsement of efficiency.

It was a bitter struggle that the Aëroplane Scouts were to witness at
Soissons, and six days of it had already passed. The earth was still
dropping on many graves of the German fallen, and yet, sprawling in
attitudes along the heights, in the deep-cut gorges of the plateau,
and across the flat valley bed were French infantrymen in their
far-to-be-seen red-and-blue uniforms, swarthy-faced Turcos, colonials,
Alpine riflemen, and bearded territorials.

At staff headquarters, in the first officer that passed near them the
boys recognized a familiar figure, no other than Colonel Muller, whom
they had first met in far-away Texas, U. S. A., on the day of the
record flight, and again in the hangar camp at Hamburg.

Billy impulsively stepped forward. "How do you do, Colonel?"

The officer instantly turned in his stride to inspect the speaker.
"Hello, Boy Aviator," was his hearty greeting. "How under the sun did
you ever get here?"

"Same old way," said Billy, "the airline, of course."

"And here's the other one," the colonel reaching for Henri's shoulder.

"By the way," continued the big soldier, "this must be a field day for
flyers. Here, Hume, come and see what the wind brought in."

The officer addressed moved at quickstep in response to this
invitation. It was the aviation lieutenant from Hamburg. He grinned
from ear to ear when he laid eyes on his former charges.

"Can't lose you if I try," he exclaimed. "Have you enlisted with us?"

"No," laughed Billy, "we're still driving cars for the good merchant
from your town," with the backward point of the thumb at Roque, who was
engaged in close confab with a group of staff members near by.

"Did you blow in with Schneider, too?" asked the lieutenant. "I just
want to say that you will bore a hole in a stone wall sometime if you
train with that fellow. Nature didn't give him red hair without reason."

"Now that you are here," broke in the colonel, "you must not be allowed
to get out of practice. I expect that one of you will have to give me a
ride along the front before long. I have lost three horses this week."

"We'll do our best to oblige you, colonel," volunteered Billy.

It was no merry jest, that ride Billy gave the colonel!

At the time, the French retained a foothold north of the river at only
one point--St. Paul--where the bridge from Soissons crosses, and this
by a perilous margin, since the bridgehead was completely commanded by
German artillery on the heights.

The battlefield entire covered a front of about seven miles, the center
and eastern flank a high, level plateau rising steeply a couple of
hundred feet from the valley of the Aisne. On the western side a deep
valley ran northward, bounded on either side by turnpikes. An airman
taking the big curve of the river would not be considered a good risk
for a well-regulated insurance company.

But it could be done--and Billy Barry furnished the proof.

When the next day broke a bloody conflict was raging between the two
turnpikes, the French infantry attack on German trenches preceded by a
terrible artillery bombardment, a storm of shell and shrapnel.

Colonel Muller beckoned Billy to his side. They stood together on the
heights from which the French had been expelled only the day before.

"My boy," was the brisk address of the officer, making a field-glass
survey of the smoke-crowned landscape, "I am going down the line, and I
am to do the distance in an aëroplane. Is it you or Schneider who will
do the driving?"

"You gave me the first call yesterday," reminded Billy.

"That was my intent, and it still holds. I was only seeking to learn if
you were of the same mind since that powder mill let loose down there."

"I well know the odor of it," stoutly maintained Billy, "and it doesn't
weaken my knees."

The young aviator, accepting the matter as settled, hastened toward
staff headquarters. "Mr. Roque," he excitedly called, "Colonel Muller
wants to try one of the No. 3's this morning, and I'm to pilot."

The secret agent lifted his eyebrows as though surprised, but he really
was not. The arrangement had already been made.

"Say, Buddy, this is rough that we can't both go; and suppose something
should happen to you?" Henri had just realized that something was up,
in which his chum was vitally concerned.

"Don't you worry, pard," consoled Billy, "it is only a little spin of a
few miles, and we'll be back in no time."

"Wish it was me," sighed Schneider, for this firebrand guessed that it
would be a red-hot journey.

As the biplane swept into the breeze current, trending to the river,
which then was running brimful, and in many places overflowing its
banks between the two armies, Colonel Muller advised Billy to keep the
machine climbing for the time being, as a terrific fusillade was in
progress in the distance of the next two miles, the shells hurtling
through the air like lighted express trains. In the three steep-sided
ravines that deeply notched the plateau on the east French troopers
swarmed like bees, and at this cover the big German guns were blindly
banging.

"We can't see much, Colonel, at two thousand feet," complained Billy.

"You would see nothing at all if we ran into one of those fragments of
shells," coolly suggested the officer, "but never mind, you will do
some diving in a few minutes."

Billy got the signal to dip at the juncture of the turnpikes, and to
hold a level and lower course along the line of battle, marked here by
infantry fighting between the seemingly crawling columns far below.

"Down!"

The colonel's order was peremptory, and Billy forthwith volplaned
toward the earth.

CHAPTER IX.

THE LUMINOUS KITE.

THE biplane had hardly scudded its length on the turnpike, when the
colonel leaped from the machine, his sudden appearance greeted by
salvos, both of cheers and an extra round of rifle discharge.

Billy sat like a statue in the machine, facing a reserve force of grim,
gray-garbed veterans standing at attention.

The front rank soldiers eyed the boy curiously, no doubt wondering that
one of his years should be serving in the capacity of a full-fledged
military aviator on a mission so supremely perilous.

Billy could not understand what Colonel Muller was saying to the
commanding officer of this regiment, but he could see the effects
rippling through the serried lines, a stiffening of attitude, a closer
grip of rifle stock and squaring of shoulders.

The column, solid and compact, the German practice of close formation,
moved with clockwork precision down the field to back the general
charge against the living wall that barred the way.

"Charge! Charge!" The cry from a thousand throats.

The forces mixed in a struggling, swaying mass, with indescribable
noises, the clashing of steel and the squealing of horses, for cavalry
had joined the fray.

Billy jumped out of the machine into the dusty road, the sole spectator
there of the conflict that raged but a half mile distant.

Colonel Muller had taken to horse and was riding furiously to rally
incoming reinforcements for the gray column.

A rattle cut into the sound ruck--the machine guns of the Germans had
turned loose, and men were mowed down like ripened corn.

But fainter now in Billy's ears grew the roar of violent contention,
alternate advance and retreat serving to shift the tide of battle
further northward, and finally stemmed by the final demonstration of
the day at Soissons bridge.

Barring the occasional wild gallop of a riderless horse down the road,
the young aviator saw no signs of life about him, and he was too far
away to hear the groans of the wounded on the sodden field now enfolded
by the gathering gloom of evening.

"I wonder if the colonel has forgotten that his carriage is waiting,"
thought Billy, trying a bit of mental cheer to relieve the strain of
his trying position.

The colonel, however, had not lost his memory along with his hat, for
even then a foam-flecked horse was bringing him back to the driver of
his aërial chariot. Mud-bespattered from head to foot, he sent a hearty
hail ahead of the pounding hoofs of his weary mount.

"Ahoy, my stranded mariner: is supper ready?"

That reminded Billy of a decided vacancy under his belt, but the glad
sight of the colonel was the best tonic for a drooping spirit.

"We will wheel this airship out of the way for a spell and have a bite
to eat in the trenches."

Concealing the biplane behind a clump of bushes the colonel gave Billy
a hand-up, and the horse cantered away with its double burden in the
direction of the slopes.

It was about 7:30 when the colonel and Billy climbed over the slippery
slopes to the line of reserve trenches, lowered themselves into one of
these holes in the ground, and it was evident that the occupants knew
how to convert a ditch into a home.

This trench had a head cover formed of cross-beams, overlaid with
branches and earth--a sure protection against shrapnel. There was a
long bench of telegraph poles, little cupboards for cartridges and kit,
and ramps for reclining chairs or couches, and drains to carry off the
rain.

"Come into our parlor, colonel," invited one of the soldiers, leading
the way into a subterranean chamber, which was warmed by a fire in an
old perforated petroleum tin.

"It is wonderful what ingenuity and labor can accomplish out of the
most unpromising material," observed the colonel.

"Made in Germany, colonel," laughed one of the veterans, "no matter
where you put them."

From the business end of the trench a hot meal was speedily produced
for the visitors, adding another touch of surprise for Billy.

"Well, my lad, we must report to the general," announced the colonel,
who had politely denied the petition of the trench veterans that he try
one of their couches for the night.

"You don't mind an air trip in the dark, do you?" inquired the colonel.

"Not a bit," assured Billy, "I've made many a one."

It was quite pitch black when the colonel and Billy rode back across
the plain, but the horse was sure-footed, and the way was fitfully
lighted by the occasional upshoot of rockets that left a long green
stream of stars, revealing the now silent battlefield and its dreadful
record of uncounted dead.

While Billy flourished an electric torch in giving the biplane a
careful look over, the colonel bestowed a playful slap on the flank of
the faithful horse, which sent the animal trotting up the road.

"He knows his number and troop as well as I do, and will go as
straight as a die to the feed trough," asserted the colonel.

"Are you ready, boy?"

"Trim as a ship, colonel."

With a flare on the compass, rising high, Billy held the nose of the
biplane in the direction of the heights that centered headquarters.

Small red sparks glowed in the trenches below, and the upper darkness
was ever and anon split by signal rockets and leaping flames of light
from countless campfires.

Billy, with the aid of the small searchlight in the bow of the
biplane, found safe landing, also insuring a sight of the colors to
the sentries, who might otherwise be tempted to take a pot shot at the
winged, midnight visitor.

Henri was the first to hear the whirr of the incoming aircraft, for
which he had for hours held an open ear.

"Here you are at last!" he exclaimed, making an open-arm break for his
flying partner. "You haven't lost an eye, or a leg, or anything, have
you?" he anxiously inquired.

"Sound as an Uncle Sam dollar, old boy," assured Billy. "But you just
bet I'm sleepy."

"I believe even Roque was uneasy about you," said Henri, as he insisted
on giving Billy's blanket a snug tug.

That the secret agent proposed to reserve the services of the young
aviators to himself thereafter and during their stay in this locality
was made manifest when he told them the next day to make ready for a
quick departure in the biplanes. As usual, he furnished no advance
particulars.

It appeared that Schneider was also to figure in the expedition in a
capacity indicated by his employment of oiling and polishing a service
rifle of the 16-shot brand, and the display of a pair of long-barreled
revolvers stuck in his belt.

"He looks like an arsenal on parade," commented Billy when the
red-haired flyer, in war-like array, passed on the way to conference
with Roque.

"There is no peaceful intent about that get-up," admitted Henri. "And
let me make another prediction," he continued, still proud of his last
previous success as a prophet, "this isn't going to be any pink tea or
garden party to which we're going."

"What a head you have," said Billy, beaming with mock admiration.

There was a decided lull in the fighting this day--the ninth since the
continuous combat had been commenced, as the soldiers of the two armies
were apparently resting on their arms. Some fresh planning, no doubt,
was in progress.

The boys wandered around the camp, restlessly anticipating the expected
summons from Roque. The latter, however, had not picked daylight in
which to operate, for it was long past nightfall when Schneider sought
and advised the boys that the starting time had arrived.

The moon was working full time when the biplanes set their course,
following the turnpike toward La Fere.

Above a farm, which had practically been razed, and on the edge of a
ruined district, both Roque and Schneider signaled the pilots to lower
the flight, and the biplanes circled groundward, landing near a row
of stunted willow trees. They showed no lights, and with the motors
silenced lay hidden behind a huge pile of debris, close to a wrecked
dwelling, so close that the full moon shining through the shattered
roof gave the aviators a dim vision of hopeless confusion, cooking pots
and children's toys, broken clocks and tables, knives, forks and books
strewn on the floor, beds and everything awry.

Billy and Henri had as yet no inkling of the purpose of this mysterious
proceeding in which they were engaged. Their companions did not seem to
be in a hurry, either, to enlighten them. Roque and Schneider appeared
intent in upward gaze, perhaps hoping that the moon and a dense bank of
clouds forming near would soon come together. As a matter of fact, a
total eclipse of the great orb above did follow, with the effect of the
sudden blowing out of the one lamp in an otherwise dark room.

Curious to relate, it was not long until the moon was replaced in the
now black canopy by a small but quite silvery brilliant imitation of
the big illuminant.

The diamond-shaped light in the lowering sky flashed this way and that,
as if responding to the manipulation of an aërial cable.

Roque was not puzzling about the appearance of the dancing light; it
was the message that it conveyed which baffled him, sent, as it were,
from within the German lines, and, maybe, of vital concern--aid and
comfort to the enemy.

Sentries on the heights had reported night after night of this queer,
intermittent flashing in this very place, and when Roque heard of it,
he instantly comprehended the meaning.

Some spy within the lines was using a luminous kite to signal
information of value to the foe.

This is what had brought the secret agent, an adept in the same kind of
game, flying through the night to scotch the play and the player.

Roque and Schneider skirted the ruins, and stumbled over the plowed
ground with all the haste that such rough going permitted. The boys,
free of any order to stay where they were, cautiously brought the rear.
They were mighty curious to see what was going to happen.

Schneider had taken the electric torch from under the pilot's seat in
one of the biplanes, and it had occurred to Billy to follow suit.
This precaution served to save the party an ugly tumble or two into
forbidding ditches.

The still-hunters had just emerged into a road with a wonderful avenue
of trees. The kite telegrapher's hidden nest was near at hand. The
position of the kite itself indicated that.

A streak of moonlight breaking through a cloud-rift revealed Roque and
Schneider kneeling in the road, and there was a glint of a leveled
rifle barrel.

The boys backed up against a tree, expecting momentarily to hear the
whip-like crack of the gun. But instead came the bark of a dog--one
shrill yelp, then silence again.

The luminous kite, unleashed, followed the moon into the clouds. Roque
and Schneider dashed forward, but for nothing else than to use the
electric torch in locating a half-loaf of bread, some cheese crumbs and
a ball of cord.

The sentry dog had saved its master!

"Nothing to be gained in chasing that fox to-night," growled Roque.
"He's deep in the brush before this."

"I'd like to have got a pop at the dog, at least," complained
Schneider, patting the stock of his rifle.

The boys having no desire to be the victims of any mistake of identity,
marched forward, Billy waving the electric torch, and calling to Roque:

"It's us."

The passwords were unnecessary, for Roque knew all the time the boys
were trailing him, but was restrained from objecting by fear of some
word reaching the ear of the man they were stalking.

"You gadabouts," he admonished, "you should have been guarding the
biplanes instead of prowling around in the dark like this."

The tone of the reprimand, however, was not one of great severity. The
boys had disobeyed no order, for none had been given.

"As soon as day breaks," said Roque, as they plodded wearily down the
road, "we will continue the hunt in the machines, though I doubt very
much whether it will amount to more than a waste of time."

"If I see a man with a dog underneath us, just bring me within rifle
shot, young man, and I will show you something fancy in the way of
gunning."

Henri, whom Schneider was addressing, mentally resolved that he would
be in no haste to perform as suggested.

Conditions, however, were reversed long before this test could be made.
Indeed, the reversal, with the dawn, was at hand. The hunters were the
hunted.

The thud of iron-shod hoofs, the clank of sabers--a troop of cavalry
charging through the wooded avenue--four madly racing footmen in the
furrowed field.

Full two hundred yards between them and the biplanes!

CHAPTER X.

THE CARRIER PIGEONS.

Billy and Henri, with much less weight to carry than their stalwart
fellow fugitives, and much spryer as sprinters, easily led in the race
to the flying machines.

Schneider stopped more than once in his tracks to fire from the hip at
the pursuing cavalrymen, but he failed to score a hit until the leader
of the troopers had almost ridden him down. One of the long-barreled
revolvers emptied the saddle of the rearing charger. Schneider had
thrown his rifle away at the last moment, finding his pistol more
effective in close quarters.

By this time, the boys, assisted by Roque, who was doing some shooting
himself, until all of the cartridges in the revolvers he carried were
exploded, had pushed and dragged the biplanes into the road, and ready
for the getaway.

Schneider, with a yell, hurled the empty revolvers in the direction of
the next comer, then bounded across the first ditch in his way, jammed
a shoulder against the now humming machine in which Henri was seated,
to give it starting impetus, and at the same instant leaped within the
machine.

Both machines were off in a jiffy, and when the cavalrymen in force
galloped to the spot, their carbines fell short of range. That they had
been chasing airmen was something of a surprise for if they had not
been so sure of a capture, the troopers would probably have pumped lead
much earlier in the chase.

"Guess he didn't get his man for keeps," remarked Billy to Roque, as a
side turn of the aircraft enabled him to look down on the field, where
a dismounted rider was getting a helping hand up from a comrade.

"Schneider gave him something to remember, anyhow," grimly replied
Roque.

In the other machine the red-topped and red-tempered aviator in the
observer's seat was deeply deploring, in no uncertain terms, the loss
of a crack-a-jack rifle and two up-to-date revolvers, borrowed for the
occasion.

"Hume may toss earth when I tell him his pet irons are gone, but it was
a shindy for quick action, and no saving grace."

Schneider evidently intended to tell the aviation lieutenant about the
fight before he mentioned the missing weapons.

The next flight planned by Roque was one of long distance--starting
twenty-four hours later, and leaving France.

"Good-bye, my young friends, and good luck to you; if you ever see
Colonel McCready again tell him 'here's looking at him.'"

These were the parting words of Colonel Muller, accompanied by a warm
hand-grip.

When the flying party finally reached Strassburg, the big German city
of the Alsace-Lorraine region, it was a glad day of halting.

They had floated in over a country literally shot to pieces by the
concentrated fire of the French and German guns--that is, in French
Lorraine--and in the distance viewed the great fortress of Metz. To the
aviators it appeared as though the land hereabouts had been devastated
by a gigantic earthquake, which had shaken down all the towns and
villages into a mass of shapeless, smoke-blackened ruins.

The boys wondered that they did not see more soldiers in the open, and
Henri expressed this wonder to his companion in the biplane.

"Oh, but the woods are full of them," assured Schneider, pointing to
the small columns of smoke rising here and there from the snow-clad
forests.

True it was that these same woods contained thousands and thousands
of armed warriors, ever on the lookout, who were gazing across the
frontier at the other woods, which concealed countless thousands of
soldiers of the Kaiser.

In Strassburg, Roque was again in touch with the invisible strands of
the far-spreading web he maintained. Among his first advices was the
most disturbing one that Ardelle had returned and had been making some
ten-strikes within the borders of the empire.

The boys shrewdly guessed that something of the sort had happened from
the renewal of the German agent's habit of charging almost every sort
of disaster to the secret work of his French rival.

Roque realized, as one of the profession, what an important factor is
the under-cover man who works within the enemy's lines in the service
of his country. And with a keen blade like Ardelle, big things were
possible, as past performances indicated.

But even Henri, as a self-claimed prophet, had no idea that the man
he knew as Anglin would bob up in Strassburg, though the city was as
likely a point as any in the war zone for secret service activity.

When Billy jokingly asked his chum if he had any predictions to fit
this occasion, Henri admitted that his second-sight "was off the job."

It soon developed that the secret service experts of both sides were
matching wits in this quarter. Reported in Roque's calendar of the
week was the giving away by one of his workers in hostile territory of
a French attack on the Germans during a fog, with the result that the
intended surprise resulted in a rout, and the assailing force mowed
down almost to a man. The mute testimony was in a low-lying valley out
in the Lorraine field--700 graves in a space 200 yards wide and about
50 broad.

Then a counter-move, wherein the French had advices from some source
unknown of the coming flight of a Zeppelin out of the Black Forest,
and three French aëroplanes were ready to charge at the big dirigible,
which, after a continuous exchange of fire lasting forty minutes, made
narrow escape to the north, just when the lighter craft had succeeded
in getting above it for a finishing stroke.

As it came about, and in a queer way, too, the boys were the first to
blunder upon a cunning ruse being resorted to by a smooth worker in
getting away information under the very nose of the astute Roque.

Billy and Henri, indulging their liking for high places, and having
a little leisure to look around, found a favorite perch in one of
the famous towers of Strassburg. They were interested, as airmen, in
watching the daily flying exhibit of the pigeons 'round about.

"Have you noticed, Henri, the streak of feathers every once in a
while that don't stop to associate with this housekeeping bunch? I've
seen two of these birds already this morning; they act just like an
aëroplane, circle about, and then break away like a bullet. There's one
now. Look!"

Henri followed the aim of Billy's finger, and, sure enough, a
long-tailed flyer was cutting the air like greased lightning in a
straight line west, without the slightest notice of the many of its
kind pluming themselves on neighboring towers and housetops.

"They make long visits," commented Billy; "I've watched, but never see
any of these air hustlers come back."

"That's funny," observed Henri, "let's borrow a glass this afternoon
and find out, if we can, where they start from. Why, this is good
sport; we'll be wearing badges next as pigeon detectives."

The boys had small notion then that they were butting into a real
business proposition, but one that did not advertise!

They were just curious to find out from where came the busy birds that
would not take time to visit with their brothers and sisters.

The most that the tower observers could discover, even with the field
glasses, borrowed without leave from Roque's traveling outfit, was
that the next bird comer took its bearings over a red-roofed building,
rising out of a circle of tall trees, a full mile to the east.

Had it so happened that Roque was in a social mood, and the boys making
him a confidant of their bird study diversion, there would, without
doubt, have been no delay in striking at the heart of the problem--and
everything else under that red roof.

Carrier pigeons were not beneath the notice of the big man with the
delicate touch!

But Roque was not inclined at the time to indulge in fireside fancies.
He was hooked up to a procession of events that needed constant
attention, and as it was all ground work for the present, he had no use
for aviators.

So he missed the first bang at the very musser-up of his plans whom he
was, day and night, seeking to locate.

"We'll amble out that way to-morrow and learn how to break pigeons of
the loafing habit."

Billy had once had a loft full of pouters in Bangor, that, he claimed,
ate their breakfast in bed!

"We'll shake Schneider and start early."

Schneider had been detailed by Roque to keep an eye on the boys, but
Henri felt sure that this firebrand would not be interested in pigeons,
save in a potpie, so he suggested the "shaking" process.

Trained in the sense of location by their aviation experience, the
boys proceeded without difficulty to the sparsely settled neighborhood
of the red-roof, which they found to be in the center of a neglected
garden, overgrown with weeds.

"Don't see any pigeon loft yet?"

Having been a fancier himself, Billy knew how the birds were housed.

"You might also say that you don't see any pigeons," added Henri.
"We've surely run by the station."

"Not on a little excursion like this," maintained Billy. "This is no
ghost story."

With the words he led the way up the long gravel walk extending from
the rusty iron gate to the front of the house.

"What will we tell them?" he asked, reaching for the brass knocker on
the dingy door of the dwelling.

"How will it do to say we are from the gas office?"

"A fool answer fits a fool's errand," agreed Billy as he gave the
knocker a sounding rap.

The pounding awakened no sign of life.

"Come on, Billy," urged Henri, "let's go. It's all a crazy move,