After the sudden death of her parents in an accident in 2012, Claire Kirkland, a young New York artist, finds in the files of her mother, Valerie, a detailed account of her experience of being marooned for a year on a remote Indonesian island with another woman. Claire sends the papers to her cousin for inclusion in a family history he is preparing; she doubts they will be of much interest to anyone outside the family.
Part One of the story is Valerie's account of her experiences. An intelligent, neurotic journalist, she has accompanied her lawyer husband, Nick, on a Bar Association jaunt to Bali. On the plane they meet Nick's Harvard Law School classmate Tim Winthrop and his pregnant wife, Rosemary.
The two couples charter a seaplane to explore Bali and the thousands of islands surrounding it. They land in a lagoon and picnic on an uninhabited island. As their plane is taking off afterward, it crashes in the ocean. Tim and the pilot are lost, but Valerie manages to drag the unconscious Rosemary to shore.
Nick also swims to the beach, but his leg has been shattered in the crash. As his condition deteriorates, the acrimoniousness of his marriage to Valerie becomes evident. He resents her taking charge of the situation, but she realizes that their survival depends on her. She braves the island's jungle-like interior to find food and water, and drags back to the beach materials to construct a primitive shelter from the sun. Rosemary, in the eighth month of her pregnancy, comforts Nick as he becomes delirious and finally dies.
Valerie, torn by guilt at being unable to help or comfort him in his final agony, puts off burying him, even though the smell of decay has become very strong. Just as she is ready to start digging a grave, three eight-foot-long dragon lizards slink out of the tall grass and devour his body as the two women cling to each other, terrified.
Though both women are in shock, they now realize that they may be stranded here for some time, and they begin doing what they can to prepare for the birth of Rosemary's child. Despite bouts with malaria and terror of the dangers surrounding them, Valerie puts on a brave front and assists at the birth of Rosemary's son. Though both women are now suffering from a cyclic form of malaria, the child is healthy and strong and full of eager curiosity.
When Timmy is three months old he is bitten by a scorpion. He goes into cardiac arrest and is saved by Valerie's application of CPR techniques She is feeling more and more proprietary toward the boy, seeing herself in a fatherly role and nursing romantic fantasies about Rosemary. She uses her control over the situation to pressure Rosemary into a sexual relationship, and Rosemary finally capitulates.
In Part Two the story is picked up by Rosemary, whose account of their island experiences was included with Valerie's papers. Rosemary's ambivalent feelings toward Valerie become evident, as does the contrast in the two women's backgrounds. Rosemary is part of a large, loving Boston family, while Valerie is estranged from her mother, her only living relative. Despite feelings of sinfulness over indulging the sexual feelings Valerie has awakened in her, Rosemary finally accepts the relationship, realizing that Valerie's devotion at least enhances her own and Timmy's chances for survival.
The three live through various trials on the island--including the annual monsoon, an earthquake, and a tidal wave. By the time Timmy is able to say a few words and make tentative efforts to walk, they have become a kind of nuclear family.
At this point they are rescued by two biologists who have come to the island to explore the habitat of the giant dragon lizards.
Part Three of the story describes what happens when the women return to civilization.
