Among the cadets who wished to become a captain was one named Gabe Werner, a great chum at that time of a lad named Bill Glutts. Having failed of election, Werner did all he could to make things uncomfortable for the Rovers, and in his actions he was aided by Glutts. But these two young rascals were discovered in some of their nefarious doings, and, becoming alarmed, Gabe Werner left the school camp and did not return. Glutts was brought before Captain Dale, the teacher in charge of the camp, and received a stern lecture and was deprived of many liberties. While the Rover boys were at Colby Hall the great war in Europe opened and our country was overrun with German spies and sympathizers. During their time under canvas the boys made several surprising discoveries, and in the end helped the secret service men to capture a hidden German submarine. They likewise helped to round up the fathers of Nappy Martell and Slugger Brown. Mr. Martell and Mr. Brown were sent to prison on the charge of aiding the enemy, while Nappy and Slugger were marched off to a detention camp in the South. When being taken away Nappy and Slugger were very bitter against the Rovers, and vowed they would square accounts the first chance they got. "And they will do it, too. You'll see," was Fred's comment. "They are as mad as hornets, and they will do everything they can think of to make trouble for us." When the call for army volunteers came Dick Rover and his brother Sam had lost no time in enlisting. At first Tom Rover had been unable to get away. But soon the business in New York City had been left in reliable hands, and the three fathers of the boys had gone to the trenches in Europe to do their bit for Uncle Sam. They had been in several engagements, and Tom and Sam had received shell wounds, while Dick Rover had suffered somewhat from a gas attack. "Well, we can be thankful that it is no worse," had been Jack's comment on receiving this news from abroad. "Just the same, I wish this awful war was at an end." During the Winter Gif Garrison had received a letter from his uncle stating that he and his chums might use a bungalow up in the woods known as Cedar Lodge. Gif at once invited Dick Powell, often called "Spouter" because of his fondness for long speeches, and the Rover boys to become his guests on an outing to the lodge. And how all of the lads went to that place has been related in detail in the volume previous to this, entitled "The Rover Boys on a Hunt." In that book they came upon a house in the forest, and there uncovered a most unusual mystery. They found that some Germans were getting ready to establish a wireless telegraph station, and aided in the round-up of these men by the United States authorities.