Nester Patou, a naive police officer, is transferred to the red light district in Paris and organizes a raid on a dodgy hotel running as a brothel. In doing so he inadvertently disrupts the corrupt system of the police and the pimps union, and even nets his station superior. Fired from his job, Nester goes to the local bar for a drink and befriends a pretty young lady named Irma la Douce. Upon realizing she is a prostitute, Nester invents a crazy scheme to keep her from seeing other men.