Walter takes a flight from New York City to Venezuela. He has just ended his relationship with his married mistress, Ivy. On the plane he meets a German man named Herbert. On the plane's layover, Walter almost decides not to get back on the plane, but when the flight attendant discovers him still in the airport, he continues on the flight. Walter first mentions his recurring stomach pains.
The plane crashes in the Sierra Madre desert, but no one is hurt. Walter discovers that Herbert is the brother of an old friend, Joachim, whom Walter has not seen since he left Zurich, Switzerland, several decades ago. He also learns that Joachim married Walter's old girlfriend, Hanna, and they had one child together. Hanna and Joachim are divorced now, and Herbert does not know anything about her present life. During this section it becomes clear that Walter is retelling this story from the future, and he frequently interjects comments about past events. He reveals that when he left Zurich, Hanna was pregnant with his child. It seems clear that the child Herbert thinks was Joachim's may actually be Walter's.
After they are rescued and land in Mexico, Walter decides to postpone his business in Venezuela. He decides to travel to Guatemala with Herbert to see Joachim. Joachim is running a tobacco plantation for the same company that employs Herbert. Herbert has not heard from his brother in months, so he is going to see what has happened to him. Herbert and Walter travel by train to the city nearest the plantation. The journey is very rough, and Walter almost turns back several times. Once at the town, they still cannot reach the plantation because the town only has one jeep, and it appears to be unavailable. Walter and Herbert are overcome by this obstacle for several days. Finally, another tourist, Marcel, learns of their problem and offers to secure the jeep for them. He wants to go with them to see some interesting Mayan ruins. As these details are worked out, Walter thinks about the manner in which he left Hanna. He determines that he did not do anything wrong in his behavior towards Hanna. Their drive is very difficult, and they almost give up. Finally, they come upon the tobacco plantation.
As soon as they arrive, they learn that Joachim hanged himself several months ago. The body is untouched, so they film it and bury it. Walter and Marcel leave, but Herbert insists on staying and taking over Joachim's job. Walter wonders how exactly Hanna and Joachim wound up marrying. He also wonders when Hanna decided to have their baby.
Walter goes to Venezuela, but the engines that are supposed to have been assembled are not ready. He returns to New York, but he does not know what to do when Ivy meets him and wants to continue their relationship. Finally he arranges to leave for Paris the next day by ship instead of a week later by plane. On the boat, he sees Sabeth, his daughter, for the first time (though he does not know she is his daughter). Over the week they slowly become acquaintances and almost friends. She spends a lot of time with a young man whom Walter assumes is her boyfriend, but eventually Walter stops noticing him. On their last night on the ship, Walter asks her to marry him, but it is unclear whether or not he is serious. They part without really saying goodbye. On the boat Walter's stomach pains have become progressively worse, and he decides to see a doctor in Paris.
Walter is in Paris to go to a series of conferences related to his job at UNESCO. But he clearly wants to see Sabeth again, so he goes to the Louvre every afternoon. He expects Sabeth will be there, because on the ship she could not believe that he had never been there. One afternoon he does meet her, and they have coffee. He arranges to take her to the opera that night. Then, he offers to drive her to Rome, and she accepts. The narrative continues to periodically shift into the future, where Walter continually returns to the idea that coincidence rather than fate drove these events. He emphasizes that he had no way of knowing that Sabeth was his daughter.
Walter and Sabeth drive through France and then Italy together. After they reach Avignon, during a lunar eclipse they share a passionate kiss. That night Sabeth goes to Walter's room, and they sleep together. Thereafter they continue to occupy separate hotel rooms. Walter is uncertain of the status of their relationship. Sabeth's need to visit every museum, monument and monastery they pass creates tension, since Walter does not appreciate or enjoy art.
At dinner one night Sabeth talks about her mother, and Walter does not consciously notice anything significant. But the next day at the Via Appia, Walter begins to question Sabeth about her mother. After a little while Walter realizes that Sabeth is Hanna's daughter, and Sabeth realizes that Walter used to know her mother. Walter does not think that Sabeth could be his daughter. He asks her whether he is the first man she slept with, and she tells him that she had two previous lovers. That night in Rome Sabeth becomes upset about Walter's response to her confidence, and he reassures her, but nothing else happens. From the future Walter reflects on the nature of his guilt. He emphasizes that Sabeth initiated the sexual component of their relationship.
The narrative skips forward in time. Walter wakes up in a hospital in Athens. Hanna is there. She remembers Walter, and she has learned that he is the man traveling with her daughter. Walter remembers what happened: Sabeth was bitten by a snake, and he managed to get her to a hospital in Athens, though it took a long time. Walter learns from the doctor that the snake bite is very unlikely to be fatal. Hanna takes Walter home with her.
Over the course of the evening, Walter manages to avoid telling Hanna about his relationship with her daughter, and at first she insists that Joachim is Sabeth's father. They argue, and Hanna is clearly very angry that he was with her daughter. Just before they go to bed, Walter finally tells her about Joachim's death in order to avoid telling her he slept with her daughter. Hanna is very upset, but for some reason Walter cannot leave her without admitting he slept with Sabeth. Hanna says almost nothing. As Walter tries to sleep, he realizes Hanna is sobbing loudly. She won't let him into her room, but he breaks down the door. She still will not speak to him.
Alone in Sabeth's room, Walter recalls Sabeth's accident more clearly. They had decided to spend the night out of doors and had wound up walking all night because of the cold. The next day, Hanna has already been to see Sabeth when Walter wakes up. They talk more in the morning, and Walter kisses Hanna, but it only makes her angry. They drive to the beach where Sabeth was bitten in order to retrieve Walter's things. On the beach Walter tells Hanna exactly what happened to Sabeth, and Hanna tells Walter he is Sabeth's father. At the hospital Walter and Hanna learn that Sabeth has died, not from the snake bite but from an undiagnosed skull fracture that she received in a fall after the snake bit her.
The narrative again jumps ahead, and Walter is back in the hospital in Athens. He is keeping a journal. He writes about how he left Athens for New York, where he discovers he is very unhappy with his life. Walter is in the hospital to have an operation to fix his stomach. He is afraid he is going to die, and he wants to make up with Hanna for Sabeth's death. We learn that from New York, Walter flew to Venezuela to complete the same business from his previous trip. On the way he went to see Herbert and could not understand that Herbert did not want to leave the plantation.
In Venezuela, he tries to work, but his stomach gets much worse, and he cannot. In the hospital Hanna visits Walter. Hanna begins to discuss Sabeth with him. Walter is becoming more and more afraid that he is dying.
Walter leaves Venezuela and flies to Europe by way of Cuba. He winds up staying in Havana for four days. He writes letters to Hanna and thinks about Sabeth. He loves Havana and feels very happy, but then his stomach pains return worse than ever.
Back in the hospital, Hanna has begun to wear white instead of black. She confides in Walter about her own past experiences with a much older man. She tells him about giving birth to Sabeth and about her problems with Joachim.
Switching back to Walter's journey, Walter travels from Cuba to Germany. He visits Herbert's company, because he feels he should tell them about Joachim's death and show them his films. While he previews the films to find the correct ones, he winds up viewing several films of Sabeth. He gets upset and walks out, leaving the films behind. He takes a train to Zurich, and he thinks about putting out his own eyes so that he can stop picturing Sabeth.
Walter stops in Zurich simply because he he has not been there in years. He runs into his old professor, whom he had also bumped into after having coffee with Sabeth in Paris. They have a drink, and his professor casually refers to Sabeth as Walter's daughter. Afterwards, Walter immediately leaves Zurich for Athens. Hanna meets him at the airport.
Walter visits Sabeth's grave and then goes to hospital for tests. They insist on admitting him, and he begins his wait for an operation. Walter writes Hanna several letters. He makes the necessary preparations for his death. He remembers that earlier that day, Hanna told him what she did immediately after Sabeth's death. She also told him many more details about the end of her relationship with Joachim and her life with Sabeth. Walter apologized to Hanna for his behavior, but Hanna insisted on apologizing to Walter for the way she acted when she became pregnant. She believes that Walter left because he knew that she did not want to share their child. Walter thinks about the fact that Hanna will never totally recover from Sabeth's death. Walter's journal ends when they come to take him to the operating room.