Alphonse Tram (Gérard Depardieu) finds a corpse on the Paris Metro, and -- inexplicably -- the murder weapon is Tram's misplaced pocketknife. Tram attempts to contact the authorities, but alcoholic police detective Morvandieu (Bernard Blier) couldn't care less. Then an eccentric killer (Jean Carmet) befriends Tram, and the two recruit Morvandieu to join them as they commit a series of brutal crimes in a frustrated attempt to punctuate their otherwise boring lives.