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