Distraught when her middle-aged lover breaks a date with her, 21-year-old Toni Simmons (Goldie Hawn) attempts suicide. Impressed by her action, her lover, dentist Julian Winston (Walter Matthau) reconsiders marrying Toni, but he worries about her insistence on honesty. Having fabricated a wife and three children, Julian readily accepts when his devoted nurse, Stephanie (Ingrid Bergman), who has secretly loved Julian for years, offers to act as his wife and demand a divorce.