While cleaning the office of a detective agency, janitors Laurel and Hardy answer a telephone call from an inventor who claims to have created a destructive bomb he calls "The Big Noise." Posing as detectives, the duo move into the inventor's home, where they must contend with his eccentric behavior, oddball widowed aunt (who takes a fancy to Hardy) and his misbehaving nephew. The inventor's neighbors are crooks who are eager to steal the new bomb.