Wealthy businessman Stephane Margelle (Jean-Paul Belmondo) may be married, but he's always on the lookout for another woman to bed whenever his wife, Sophie (Marie Laforêt), is away. When Sophie returns home unexpectedly one afternoon and finds Stephane in bed with his mistress Julie (Sophie Marceau), he attempts to convince her that the girl is his daughter from a previous marriage. Sophie then calls her husband's bluff and invites Julie to move in, forcing Stephane to keep up his charade.