The armistice was signed and the Army Boys assigned to the Army of Occupation with headquarters at Coblenz. At Luxemburg while on the march they came across an American family who for business reasons had lived for a time in Coblenz. How they took the head of the family for a German spy, how they marched as conquerors into Germany, how Frank was cheered by learning that his mother's property was sure to come to her, how Bart was found and restored to his right mind, how by the aid of the suspected spy who turned out to be a patriotic American they thwarted a desperate German plot to blow up the fortress of Ehrenbreitstein on the Rhine--all these and other thrilling adventures are described in the fifth volume of the series, entitled: "Army Boys Marching Into Germany; Or, Over the Rhine With the Stars and Stripes". Since the Army Boys had served as night patrol, they were exempt from getting up when reveille sounded the next morning, and the sun was some hours high when they found themselves together again in their favorite spot in front of the great fortress of Ehrenbreitstein, which formed the principal barracks for the American troops in the occupied zone. "Well, Mister Detective," said Billy, with a grin, as he slapped Frank on the back, "have you figured out any dope about the fellows who came so near to bumping us off last night?" "Can't say that I have yet," laughed Frank. "Fact is, I was so dog-tired when I hit the hay last night that I went to sleep the minute my head touched the pillow. And so far this morning I've been so busy packing away grub that I haven't had time to think of anything else. But if I can get leave I'm going over to Coblenz today and take a look at that alley." "Here comes the corp," remarked Bart, as he saw Wilson approaching. "I wonder whether he found out anything further about last night's rumpus." "Nothing at all," answered the corporal, who heard the last words. "Everything was quiet for the rest of the night. I stationed two of the men close to the alley with special directions to watch it, but nothing at all happened that was out of the ordinary." "It's hardly likely that there would," answered Frank. "They wouldn't be likely to try the same game twice in the same night." "Perhaps they had some special grudge against one or all of you fellows," suggested the corporal. "Have any of you made any special enemies in the town that you know of?" "I don't think so," replied Frank. "How about it, boys?" "Not guilty," laughed Billy. "We've yanked in a few trouble makers from time to time," said Tom thoughtfully, "but we weren't any rougher with them than we had to be." "I'll tell you!" broke in Bart, as a thought struck him. "It was our bunch that discovered the plot to blow up Ehrenbreitstein and got the tip to our people just in time. Perhaps that's made some of these crazy Huns wild to throw the hooks into us."