Marine Lieutenant Steve Landers has perfected a new bomb-release for airplanes which he is testing with the aid of his mechanics,'Singapore' Stebbins and Jack Murray. Dick Weber, one of a group of enemy agents attempting to steal the plans, is a friend of Colonel Dale, whose daughter, Linda, is engaged to Landers. Weber learns that "Singapore" and Jack are to deliver the final blueprints to the Colonel's home. Beckstrom , head of the spy ring, has some of his agents dress as Marines and obtain entry the the hangar. They get the plans but "Singapore" and Jack have overheard a conversation that indicates the spies are heading for a nearby island which is the headquarters of the espionage group.