oking for some signature.

"No name attached, Jack?" asked his chum.

"Nothing whatever to tell who wrote that warning. Here, take a look at
it, Tom. Your eyes may be sharper than mine and see something I've
missed."

But Tom and the other pilot both failed to throw any light on the matter
after examining the paper thoroughly. They exchanged stares. Then Jack
laughed, a little queerly.

"This is certainly a mystery," he went on to say, trying to take the
thing as a joke. "Some kind friend sends me a solemn warning, and then
neglects to sign his name. Do you think any of the fellows of the
escadrille could be up to a prank?"

Tom shook his head. The other pilot also exhibited positive signs of
doubt in connection with such a thing.

"The boys often have their little jokes, and we are a merry bunch much
of the time, just to change off from the nervous strain we're living
under," the man observed. "But I'm sure not one of them would dream of
doing a thing like this. It would be a mean trick."

"Then both of you are inclined to believe this warning was meant in all
seriousness, are you?" continued Jack, no longer grinning as before.

"Yes, I do," Tom instantly announced. "It seems a bit childish, sending
it in such a queer fashion; but then perhaps it was the only way open to
the person. There was one chance in ten that it would be found; but you
know sometimes we can't choose our way of doing things, but must
accommodate ourselves to circumstances. This toy balloon being handy
suggested a possible way of getting the warning to you, Jack."

"But why me any more than you, Tom, or any other fellow in the
escadrille?" continued Jack, sorely bewildered.

"That's something we can only guess at," he was told. "Evidently this
person had your name, and knew you were working here with the Lafayette
boys. Try to think of some one you may have done something for to make
him feel grateful to you. Could it have been that boyish-looking German
prisoner we talked with the other day, and for whom you bound up a badly
damaged arm, Jack?"

"Oh! that boy!" exclaimed the other, and then shook his head. "No, it's
impossible. You see the poor chap could hardly talk halfway decent
English, and I'm sure he never could write my name like this. Besides,
Tom," Jack went on triumphantly, "I never bothered to mention to him
that I had a name. To him I was simply an American flying for France."

"Anybody else you can think of?" persisted T