Rene is a cynical veteran of the Montmartre police department with a belief that everyone is guilty of something. He'll also take payoffs from anyone, including criminals in exchange for their freedom. His young partner, Francois, has begun to share Rene's less than upstanding practices, but really enjoys being a cop and hopes to someday become lieutenant. Everything is running smoothly until, one day, Rene and Francois perform a good deed. Responding to a robbery alarm, Rene anticipates the thief's route, and the culprit runs right into the detective's arms. Rene is prepared, as usual, to split the loot 50-50 with Francois and free the thief. But Francois insists on returning the cash. He returns the money directly to the shop owner and gallantly asks for no receipt. Unfortunately, the shop owner is a former girlfriend of Rene's with a serious grievance, and when the thief is recaptured empty-handed, she accuses the detectives of taking her money.