153
XX. Jack Climbs a Wall 162
XXI. In the Old Lorraine Chateau 171
XXII. Facing More Difficulties 181
XXIII. Left Behind in the Enemy's Country 191
XXIV. Troublous Times for Jack 200
XXV. Back to Safety--Conclusion 208

AIR SERVICE BOYS OVER THE ENEMY'S LINES

CHAPTER I

BACK OF THE TRENCHES

"Tom, what do you suppose that strange man who looked like a French
peasant, yet wasn't one, could have been up to late yesterday
afternoon?"

"You mean the fellow discovered near the hangars at the aviation camp,
Jack?"

"Yes. He seemed to go out of sight like a wreath of smoke does. Why, if
the ground had opened and swallowed him up, once the hue and cry was
raised, he couldn't have vanished quicker. I wonder if what they say
about him can be true?"

"That he was a German spy? Anything is possible in war times."

"I guess you're right there. German secret sympathizers, and spies in
the bargain, seemed to bob up all over the United States before we
crossed the ocean to do our fighting for France as aviators."

"They certainly were busy bees, Jack, blowing up munition-works, trying
to destroy big railroad bridges so as to cripple traffic with the Allies
over here; burning grain elevators in which France and Great Britain had
big supplies of wheat stored; and even putting bombs aboard ocean liners
that were timed to explode days later, when the boat would be a thousand
miles from land."

"Over in France here they make short work of spies, I've heard, Tom!"

"Yes, it's a drumhead court martial and trial. Then, if the man or woman
is found guilty, the spy goes out with a firing squad to the most
convenient stone wall. They never return, Jack."

"Whee! that sounds like war times, doesn't it? And to think the two of
us are right on the firing line, in the midst of all the scrapping. But,
Tom, tell me, why should a tricky German spy want to hang out around the
aviation field? He could hardly expect to pick up any news there that
would be worth taking across the lines to the headquarters of the Crown
Prince before Verdun."

"Don't be too sure of that, Jack. Perhaps he might learn of some
contemplated bombing expedition, like that one we went on not so long
ago." And Tom Raymond smiled slightly.

"They are a mighty clever bunch, those spies," admi