Dr. George C. Chapman, a famous psychologist, and his assistant, Paul Radford, arrive in a Los Angeles suburb to conduct a survey on the sex habits of American women. After their first lecture on the project, four women volunteer as subjects. Sarah Garnell, a middle-aged wife and mother, is having an affair with a young theater director, Fred Linden. She decides to run away with him, but he rejects her, and she returns to her husband. Teresa Harnish, married to an art dealer, believes that they have a perfect relationship until she meets handsome football player Ed Kraski. When she discovers his rough aggressiveness, however, she turns back to the safety of her home. Naomi Shields, an alcoholic nymphomaniac, becomes involved with a jazz musician who allows his drunken friends to rape her at a party; she subsequently commits suicide. The fourth woman, Kathleen Barclay, a young widow who believes that she is frigid, breaks down during questioning and leaves the doctor's office. Paul traces her to her home and, by becoming personally involved, convinces her that her fears are unfounded. Dr. Chapman then reveals that the four cases are exceptions to the rule; most American marriages are happy ones.