Air Service Boys Over The Enemy's Lines; Or, The German Spy's Secret — Charles Amory Beach

"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."