"By the way," put in Tom, "you'd better tuck your handkerchief in a little more tightly or you'll lose it. It looks as though it were almost ready to drop out." "What if it does?" snarled Rabig. "I could pick it up again, couldn't I?" "Of course you could," said Tom, "but you might pick up something else with it. Dust, or a bit of paper, or something like that." "Say, what's the matter with you guys anyway?" demanded Rabig, glowering at them. "That looks like quite a solid door," remarked Frank, inspecting it critically. "Oh, I don't know," responded Billy. "It's got dents in it. Here's one that looks as though it were made by a rifle butt." Rabig looked at them angrily, and yet furtively, evidently seeking to find out how much their remarks meant. "You fellows had better get along," he snapped. "You're interfering with discipline by talking to a sentry on guard." Rabig's newborn reverence for discipline amused the boys so that they had hard work to repress a laugh. "You're right," responded Frank. "We'll mosey along." "Ta-ta, Rabig," said Bart. "Keep your eye peeled for any Hun trick. That fellow nearly got me yesterday with his knife, and he might try to play the same game on you." "Don't you worry," growled Rabig. "I can take care of myself." The chums passed on, laughing and talking about indifferent things, until they were out of ear shot. "We've got him guessing," remarked Billy with a grin. "We managed to put a flea in his ear," agreed Tom. "Did you see how red he got?" questioned Bart. "He sure is wondering how much we know," summed up Frank. "Whether it will make him go straight or not is another question. What we fellows ought to do is to take turns keeping tab on him, so that he can't act crooked even if he wants to." "It's a pity there should be any men in the American army whom we have to watch," said Tom bitterly. "Yes, but that's to be expected," returned Frank. "There's never been an army in the history of the world that hasn't been infected with traitors more or less." "Look at Benedict Arnold," remarked Billy. "To my mind, it's surprising that there aren't more," said Frank. "That's what the Kaiser was counting on. He thought that the German element in America was so strong that we wouldn't dare to go to war with him. Do you remember what he told Gerard? That 'there were five hundred thousand Germans in America who would revolt'?" "Yes," grinned Billy, "and I remember how Gerard came back at him with the 'five hundred thousand lamp-posts on which we'd hang them if they did.'" They were out on the main road by this time, and they stepped to one side and saluted, as an officer in French uniform, accompanied by an orderly, came galloping along. The officer's eye swept the group as he returned the salute, and when it rested on Frank he drew up his horse so suddenly that the beast sat back on its haunches.