Mathias Pascal, saddled with a stupid wife and a nagging mother-in-law, leaves home and is extremely lucky at several gambling resorts. He returns home and discovers that a drowned man, fished out of the river, bears an uncanny likeness to him and is being buried by his family as him. This, to him, is a pleasant turn of events and he goes to Rome, where he falls in love with Louise Paleari. Count Papiano, a jealous suitor of Louise's, threatens him with arrest unless he produces credentials to prove his identity.

Michel Piccoli plays a police inspector whose best friend is murdered on the orders of gang boss Charles Vanel. The inspector knows full well that Vanel is too crafty and well-connected to ever stand trial for his crime, so he carefully lays a subtle trap for his adversary. Unfortunately, both Piccoli and Vanel are thwarted by a pair of scheming females.