ve been a spy, and up to some mischief, because he slipped off
so slickly."

"I had him in mind all the while," said Tom. "And if any mischief has
been done, of course we can lay it at his door; though just how he
managed to work we'll perhaps never know."

"I caught sight of him, too," Jack remarked; "and I only wish now I'd
had a good look at the chap who owned those pigeons to-day, so as to
tell if they were one and the same, which I believe to be a fact."

Just then Tom gave his chum a kick with the toe of his shoe. This
suddenly reminded Jack that he was treading on forbidden ground, since
they had resolved not to say anything to a third person concerning the
adventure of that afternoon.

The other member of the escadrille was looking interested. He understood
that Tom and Jack must have met with some singular adventure; but since
they did not see fit to take him into their confidence he was too polite
to ask questions, feeling there must be a good reason for their silence.

Presently they arrived at the hangars. It was now almost sunset. The
fliers were coming down one by one, their labor for the day having been
accomplished. It had been a pretty arduous day, too, and two members of
the escadrille had new honors coming to them, since they had dropped
enemy planes in full view of tens of thousands of cheering spectators,
after thrilling combats high in the air.

One had also passed through an experience that few aviators can look
back to. He had started to drop rapidly when, at almost ten thousand
feet altitude, his motor was struck by a missile from a rival pilot's
gun. When halfway down, either through a freak of fortune or some
wonderfully clever manipulation on the part of the pilot, the machine
righted, and he was enabled to volplane to safety, though considerably
bruised and cut up through hasty landing.

Jack quickly had his little Nieuport out of the hangar, and the three
airmen began a minute inspection. For a short time nothing developed
that had a suspicious appearance. Jack, in fact, was beginning to
believe the warning might after all be in the nature of a fake, or else
the spy had not found a favorable chance to do his foul work before
being frightened off.

But presently Tom gave utterance to an exclamation.

"Found anything, Tom?" asked Jack eagerly.

"Yes. Come around here, both of you!"

When the others joined Tom he pointed to where an important wire stay
had been dextrously filed so