othing with which to make a fight,
they were as safely held as though guarded by a regiment.

"There goes another!" cried Jack, as a second detonation, almost as loud
as the first, shook the ground. "Some of our bombs must have been time
ones."

"No," said Tom. "What's probably happening is that the fire is reaching
stores of ammunition, one after the other. This whole place may go up in
a minute."

That seemed to be the fear on the part of the Germans, for more orders
were shouted, and all but two of the soldiers guarding the captives were
summoned away from the wire stockade.

There had been a bright flare of fire after the second explosion, but
this soon died away, and the shouts and commands of the officers
directing the fire-fighting force could be heard.

Tom and Jack were standing near the wire barrier trying to look out to
see what was going on beyond a group of ruined factory buildings, and at
the same time casting longing eyes at the great aeroplane which seemed
only waiting for them, when the two boys became aware of a figure which
appeared to be slinking along the side of the stockade. This figure
acted as though it desired to attract no attention, for it kept as much
as possible in the shadows.

"Did you see that?" asked Jack of his churn in a low voice.

"Yes. What do you make it out to be?"

"He isn't a German soldier, for he isn't in uniform. Have any of our
crowd found a way out of this place by any chance?"

"I don't know. If they have--"

The boy's words were broken off by a low-voiced call from the slinking
figure. It asked:

"Are you American, French or English prisoners?"

"Some of each variety," answered Jack, while at the sound of that voice
Tom Raymond felt a thrill of hope.

"If you get out, is there a chance for you to get away in your
aircraft?" the figure in the shadow questioned. "Be careful, don't let
the guards hear."

"There are only two, and they're over at the front gate," said Jack, as
Tom drew nearer in order better to hear the tones of that voice. "They
seem more occupied in watching the fire than in looking at us," went on
Jack.

"Good!" exclaimed the man. "Now listen. I am an American, and I was
captured by the Germans, through spy work, some time ago, in Paris. I
was brought here, and they have been trying to force me to disclose the
secret of some of my inventions.

"I refused, and was sentenced to be shot to-morrow. But to-night you
fortunately raided this