Rosemary Hoyt, a beautiful eighteen-year-old movie starlet, on vacation with her mother, arrives at a rather deserted portion of the French Riviera. There, Rosemary meets Dick Diver, a handsome American psychologist in his thirties with whom she instantly falls in love. Dick and his wife, Nicole, are exemplars of grace and sophistication, and move among a social set of similarly extraordinary people. Rosemary becomes part of this world, and in the gay times that follow, Dick begins to reciprocate Rosemary's feelings for him. Everything goes splendidly until, after an alcoholic friend of the Divers accidentally kills a man, Rosemary discovers Dick comforting Nicole, who has had a mental breakdown.
The story shifts back in time to relate the events that led up to the marriage of Dick and Nicole. Dick attended Yale, was a Rhodes scholar, and then moved to Vienna to study clinical psychology. Once, as Dick was leaving a clinic on the Zurichsee, he met the sixteen-year-old Nicole Warren, who was being checked in. The Chicago heiress had been sexually abused by her father and, as a result, had developed an acute fear of men. The two fall in love, and Dick becomes both her doctor and her husband. They travel extensively, are happy, and have two children together.
Partially on account of Nicole's relapse, the Divers decide to invest in a clinic in Switzerland. Things begin to unravel. Dick is accused of infidelity by a former patient, and Nicole, in anger, runs their car off the road. Dick learns his father has passed away and heads to America for the funeral. Upon his return, Dick meets Rosemary in a hotel, and the two consummate the aborted romance they had begun several years earlier. In the aftermath, Dick realizes his world is falling apart. He goes out carousing, gets beat up and imprisoned, and must be rescued by Nicole's sister, Baby Warren. As Dick continues to drink, he jeopardizes his position at the clinic and is asked to leave.
The Divers return to the Riviera, and Dick continues to drink and unravel, insulting old friends. Nicole has an affair with Tommy Barban and asks Dick for a divorce in order to marry Tommy. Dick readily agrees, realizing that Nicole's finally overcome her psychological condition. Dick then disappears to America, never settling down. The book ends, suggesting that he is still there.