Book One begins in June of 1925, at a beachfront hotel on the French Riviera, near the city of Cannes. Rosemary Hoyt, a seventeen-year-old star of the popular film Daddy’s Girl and her mother, Elsie Speers, are on vacation. Soon after they arrive at the hotel, Rosemary hits the beach, looking for attention and looking for love. She finds both right away in the form of Dick Diver, 34, who seems to be playing the starring role in his own beachside drama. Supporting cast members are his wife Nicole, 23, their young kids, Topsy and Lanier, and the Divers’ very fashionable friends. Nicole can tell right away that Rosemary is after her man.
At the big party at the Divers' home, Violet McKisco witnesses something shocking in the Divers' bathroom. Only Tommy Barban, the soldier, has an inkling of what this might be, and he sticks tight by Violet to make sure she doesn’t tell anyone. This leads to Tommy and Albert, Violet’s husband, having a gun duel at four in the morning. Luckily, nobody gets gunned down – both shots miss.
The Divers invite Rosemary to party with them in Paris and she accepts. While there, she tries to get Dick in the sack several times, but he refuses, even though he’s falling in love with her. His love for Nicole is deeper, though, and he’s afraid that Nicole will be hurt. There is some indication that Nicole is irritated by Dick’s friendship with Rosemary, but she is basically nice to the girl. Rosemary turns eighteen and has her first glass of champagne. She also tries to sleep with Dick.
Abe North, a talented musician and friend of the Divers has a huge breakdown in Paris and, due to a misunderstanding in a bar, ends up getting a bunch of black men in trouble. One of them gets shot in the bed of Rosemary’s hotel suite. Dick knows that if the press gets wind of this, her career will be ruined, so he hauls the guy off the bed and into the hall and gives Nicole the bloody bed sheets to wash, hide, or something (it’s not really clear).
After the body (now in the hall) has been reported to the hotel manager, Dick and Rosemary catch their breath in the Divers' suite. They don’t see Nicole, but when they hear a noise coming from the bathroom, they worry she has fallen or something and go in there to check. They find her kneeling by the tub, swaying and talking oddly. Rosemary immediately remembers that Violet McKisco saw something weird in the Divers' bathroom two weeks ago and assumes it was the same type of thing.
In Book Two we go back in time and meet the young Dick Diver. He is a brilliant and driven young man. At 28 he has a psychiatry degree, a book in the works, has been fully discharged from the military, and is, by all accounts, a promising young man. It’s the spring of 1919 and he’s headed to a Swiss psychiatric clinic to meet his friend Franz Gregarovius, a doctor who works there. And he wants to see a young lady, a patient who initiated correspondence with him after they met about a year ago.
While waiting to hear her story from Franz, Dick remembers the letters she has written to him, talking about her mental problems and flirting with him. We learn that the girl is Nicole (big surprise). Then Franz tells Dick her story. She was having mental problems and was brought to the clinic by her father, Devereux Warren, when she was sixteen. Nicole is diagnosed with schizophrenia and her doctor, Doctor Dohmler, thinks it has something to do with Devereux. When confronted, Devereux admits that he raped Nicole when she was twelve years old after her mother’s death. Devereux is ordered to stay away from her for five years and Nicole is accepted as a patient. Since she took up correspondence with Dick, she seems to be doing much better.
After hearing the story, Dick goes to meet Nicole and she flirts with him but he tries to resist her. A week later he comes back and she makes it even clearer that she’s in love with him and that she attributes her improved mental health to their relationship. He continues to resist her. When he sees her again he tries to get her to understand that he’s not the reason she has gotten better. However, his feelings for Nicole grow stronger. Dr. Dohmler tells Dick he should not pursue a relationship with her. Dick doesn’t think this is fair to Nicole, but he makes no plans to be with her. But, when he runs into her later that summer, he falls for her completely. However, her very wealthy and protective sister, Baby Warren, isn’t sure about him.
Next, we learn that Nicole and Dick get married, that he continues practicing in Switzerland, and that he publishes a book on psychiatry that does well. Nicole gives birth to a son, Lanier, and they travel a lot. Nicole has a bad relapse when her daughter, Topsy, is born. We also get some details that seem to confirm that she has some kind of multiple personality disorder. She wants to buy a big house in the Riviera (the one we see in Book One) so that she and Dick can settle down for some serious work. She wants Dick to fulfill his career goals and thinks that if she has a field of interest on which to focus, it might help her when she is having relapses. This ends back where the novel began – on the beach.
The narrative picks up where we left off at the end of Book One. Nicole and Dick are at their home on the Riviera. Dick has lunch with Rosemary’s mom and tells her that he’s in love with Rosemary. She tells him that she encouraged Rosemary to go after him. Later, he tries to talk to Nicole but they are drifting apart and he wants to be alone. At Christmas time, Dick and Nicole go to a ski lodge in the Swiss Alps. Baby Warren is there and Franz comes. Franz wants Dick to go into business with him and buy the clinic where he met Nicole. Baby thinks it’s a good idea. Nicole also thinks it’s a good idea, and finally Dick agrees.
Meanwhile, Dick and Nicole are having marriage problems and Dick is drinking too much. One day, Nicole gets a letter from a woman saying that Dick seduced her teenage daughter. Dick denies it, and says the woman is just crazy. However, Dick thinks that he did kiss the woman’s daughter, but doesn’t tell Nicole this. Nicole doesn’t believe Dick and is furious.
Nicole freaks out when they go to a fair with the kids later that day. On the way back to the clinic, she grabs the wheel while Dick is driving and tries to drive the family off a cliff. After this, Dick leaves the clinic for a psychiatric conference that he doesn’t actually plan to attend. He feels terrible about the way things are going. He loves both Rosemary and Nicole, but doesn’t know how to deal with either woman. To make Dick's life even more difficult, his father passes away. He heads to the U.S. for the funeral. He also finds out that Abe North was beaten to death in an American bar.
Dick goes to Rome, meets Rosemary, has sex with her, breaks up with her, and then goes on a drunken Italian bashing spree. Dick punches a cop and then gets beaten badly, almost to death, in a Roman prison. Baby comes to his rescue and he escapes with his life, but now Baby feels like she owns him.
In Book Three, Dick is drinking even harder and he has to sell his half of the clinic to Franz when a patient complains about his drinking. He and Nicole travel for a bit and then move back into their Riviera home. They aren’t doing well. They meet up with Tommy Barban. Nicole decides to take Tommy as a lover and feels like she is becoming healthy again as a result of her decision.
Rosemary shows up for a visit and Nicole thinks that Dick seems happy to be with her. Dick goes off with Rosemary, and Nicole and Tommy become lovers. When Dick comes back, Nicole asks him if things went well with Rosemary and Dick tells her that his affair with Rosemary is over. Tommy approaches Dick and says that he wants him to leave Nicole so they can be together. He accuses Dick of being bad for her. Dick agrees not to stand in their way, and he leaves very shortly thereafter. But first, he spends some time with the kids.
At the end of the novel, we learn that Dick and Nicole have kept in touch, that she’s still with Tommy, and that Dick has been living in America, struggling to practice. Nicole thinks that maybe he still has a chance to fulfill his dreams of being a great psychiatrist.