Having fortuitously discovered a photograph in which Marthe embraces someone unknown, Étienne Dorsay becomes jealous and imagines various stratagems to identify the lover. In the meantime, he and his friends acquire a weekend house for a very low price.
Jean Rochefort
Etienne Dorsay
Claude Brasseur
Daniel
Guy Bedos
Simon Messina, docteur
Victor Lanoux
Boulifet, dit « Bouly »
Danièle Delorme
Marthe Dorsay, la femme d'Étienne
Marthe Villalonga
Mouchy Messina, la mère possessive de Simon
Jenny Arasse
Bernadette, la dessinatrice collaborant avec Étienne