The Rovers were students at a military boarding school: adventurous, prank-playing, flirtatious, and often un-chaperoned adolescents who were constantly getting into mischief and running afoul of authority figures as well as criminals. The series often incorporated emerging technology of the era, such as the automobile, airplanes (The Rover Boys in the Air) and news events, such as World War I. In the present volume the boys are back at Colby Hall, but it is time for the annual encampment of the military school, and soon they depart for a brief season Under Canvas. This is at the time of the World War, and the lads get mixed up in the mystery surrounding a wrecked submarine.