Dick and Nicole Diver are a glamorous couple who rent a villa in the South of France and surround themselves with a circle of friends, mainly Americans. Also staying at the nearby resort are Rosemary Hoyt, a young 17-year-old actress, and her mother. Rosemary becomes infatuated with Dick and also becomes close to Nicole. Dick toys with the idea of having an affair with Rosemary.
Rosemary senses something is wrong with the couple, which is brought to light when one of the guests at a party reports having seen something strange in a bathroom. Tommy Barban, another guest, comes loyally to the defense of the Divers. The action involves various other friends, including the Norths, a frequent occurrence being the drunken behavior of Abe North. The story becomes complicated when Jules Peterson, a black man, is murdered in Paris and ends up in Rosemary's bed at the hotel, a situation which could destroy Rosemary's career. Dick moves the blood-soaked body out of the room to cover up any implied relationship between Rosemary and Peterson.
It is revealed that Captain Dick Diver, a promising young doctor and psychiatrist, while visiting his friend Franz, also a psychiatrist meets a stunning teenage patient with an especially complex case of neuroses. The patient is Nicole, whose sexual abuse by her father is suggested as the cause of her breakdown. Over a period of time they exchange letters. With permission of Franz and his superior, who believe that Dick's friendship benefits Nicoles wellbeing, they start seeing each other. As her treatment progresses, Nicole becomes infatuated with Dick, who in turn develops Florence Nightingale syndrome. He eventually determines to marry Nicole, in part, as a means of providing her with lasting emotional stability. Strong objections are raised by Nicole's sister, who believes Dick is marrying Nicole because of her status as an heiress.
Dick is offered by Franz a partnership in a Swiss psychiatric clinic, and Nicole pays for the enterprise. After his father's death Dick travels to America for the burial, and then to Rome in hopes of seeing Rosemary. They start a brief affair, which ends abruptly and painfully. Dick gets into an altercation with the police, and Nicole's sister helps him to get out of jail. Dick doesn't see how he can be the same person after such a humiliation. He gradually develops a drinking problem. After this becomes an issue with the patients, Dick's ownership share of the clinic is bought out by American investors following his partner's suggestion.
Dick and Nicole's marriage breaks down when he becomes increasingly alcoholic and pines for Rosemary, who is now a successful Hollywood star. Nicole becomes increasingly aware of her independence. She distances herself from Dick as his self-confidence and friendliness turn into sarcasm and rudeness towards everyone. His constant unhappiness over what he could have been fuels his alcoholism, and Dick becomes increasingly embarrassing in social and familial situations. Nicole enters into an affair with Tommy Barban. At the end of the book Nicole divorces Dick and marries Barban.