In this film, Laurel and Hardy are janitors. One night, while cleaning the office of a detective agency, they answer a telephone call from Alva P. Hartley (Arthur Space), an inventor who claims to have created a destructive bomb he calls "The Big Noise." Posing as detectives, Laurel and Hardy move into Hartley's home, where they must contend with his eccentric behavior and the oddball antics of his widowed aunt (who takes a fancy to Hardy) and Hartley's misbehaving son. Hartley's neighbors are crooks who are eager to steal the new bomb. Laurel and Hardy hide the bomb in an accordion and steal an airplane to bring it to Washington. However, the airplane is a remote control target used by the U.S. Army for gunnery training. Laurel and Hardy barely escape by parachuting to safety over the Pacific Ocean, and they dispose of the bomb by dropping it on a Japanese submarine.