The novel follows Hal Lindley, a middle-aged Internal Revenue Service bureaucrat in Los Angeles, as his ordinary life fractures and sends him on an unexpected journey to Central America.
Hal and his wife Susan visit a dog kennel to retrieve the pet belonging to Susan's employer, Thomas Stern, a real-estate developer who has vanished into a jungle in Belize. Susan calls her boss "T." and regards him with maternal devotion. Hal resents Stern's outsized presence in their family. At the kennel, they learn the dog is a three-legged amputee, which draws Hal's thoughts to his daughter Casey, who has been paralyzed since a car accident in her teens. Casey despises pity and insists that disability does not confer moral sainthood. The accident is the defining event of Hal's life, one that ejected him from ordinary existence and encased Casey's childhood in a golden glow of lost paradise.
Hal drives to Casey's new apartment in Santa Monica, where she ribs him about the dog as an empty-nest surrogate and mentions her new boyfriend Sal, a former Los Angeles police officer who was paralyzed by friendly fire. Sal arrives hostile, and Hal privately dismisses him as a poser.
Hal and Susan visit Angela Stern, T.'s mother, who is pleasant but cognitively impaired. Angela mentions that a small motorboat T. had been using was found empty, having drifted ashore. Susan is stunned; despite being T.'s authorized contact, she was never informed. Galvanized, Susan announces she wants to hire a private security firm to search for T. in Belize.
Back home, Hal finds Robert, a young paralegal from Susan's office, leaving through the front door on courier duty. Inside, the shower is running and the bed is warm on Hal's side. On his nightstand he finds a tiny piece of shiny plastic. He compares it against condom packaging at a drugstore, but the results are inconclusive. He recalls that when they met in 1966, Susan believed in free love, and their monogamy was assumed, never explicitly agreed upon. Later, staking out Susan's office from a parking structure, he watches through a window as Susan and Robert lean close, their heads sinking below the edge of a file cabinet. Hal is devastated.
At a monthly dinner Casey hosts for friends, Hal arrives slightly drunk and overhears Casey whispering with her friend Nancy near the kitchen. The conversation reveals that Casey's supposed telemarketing job is a cover for phone sex work. Shaken by discoveries about both his wife and daughter, Hal abruptly volunteers to fly to Belize and search for T. His real motivation is escape: from Susan's affair, Casey's secret, and the feeling that the ground beneath him has given way. He packs hastily and departs. As his taxi pulls away, Hal feels both loneliness and a growing exhilaration.
After a long ride through hurricane-ravaged countryside, Hal arrives at a coastal resort hotel in Placencia, Belize. He admits he is not really here to find anyone but to dissolve and reassemble. He visits Seine Bight, a village of the Garifuna, an Afro-Indigenous Belizean community, to find T.'s foreman Marlo, but Marlo is out. The hotel manager tells Hal that T.'s boat was found empty at Monkey River Town and arranges for him to travel there with a German family: Hans, an avionics engineer who consults for the North Atlantic Treaty Organization (NATO); his wife Gretel, a kindergarten teacher; and their two sons. In Monkey River Town, Hal learns from the brother of T.'s guide Delonn that the two men set out on a backpacking trip and the boat drifted back empty.
The next morning, Hans delivers startling news: Through his NATO contacts, he has arranged for a Coast Guard task force to conduct a search-and-rescue exercise. Hans and Gretel take Hal scuba diving. Underwater, he thinks of Casey, who as a child believed the ocean was a kingdom where she could move freely. That evening, Gretel leads Hal on a moonlit beach walk. She strips and plunges into the ocean, and when Hal follows, she kisses him. They have sex on the sand.
The Coast Guard patrol boat arrives with American servicemembers and Belizean Defence Force cadets. The grueling six-hour jungle hike yields no trace of T., though another search team locates a guerrilla training camp, which Hans considers a major success. Back at the hotel, Hal falls asleep by the pool. Marlo finds him and takes him by motorboat to a small island where T. had been building a hotel before the hurricane demolished it. Among piles of debris, a shirtless, bearded, half-emaciated man emerges from the trees. It is Thomas Stern.
T. explains what happened. On their first night out, Delonn died quietly in his tent, likely from a heart attack. T. panicked, dragged the body back to the boat, but the propeller broke. He abandoned the boat and tried to hike out, getting lost for weeks before reaching the coast. Marlo brought him to the island, where he has been demolishing his ruined hotel and dropping the debris into the ocean as an artificial reef. T. has undergone a philosophical transformation, declaring that living for money is like living for a socket wrench. He reassures Hal about Casey: "She's going to be all right. I promise" (161).
Hal calls Susan to say T. is alive. She screams with relief but grows alarmed when Hal warns that T. may want to dissolve his corporation. Abruptly, Hal tells her he saw her on the floor of the office with Robert, and hangs up. While kayaking with Gretel, he realizes he has wasted years in a daze of regret over Casey, drifting away from Susan into memories of the daughter who might have been. Susan's affair and her devotion to her job were consequences of his emotional abandonment.
Marlo brings bad news: T. has been arrested over Delonn's death after a neighbor called the authorities. Hal flies to Belize City and calls Susan from his hotel room. He apologizes for years of emotional absence. She says the affair with Robert is not important. With help from Jeff Brady, a public affairs officer at the United States Embassy, Hal arranges legal support. T. is calm, explaining he will be released once police confirm they cannot find Delonn's body. At a party that evening, a young Air Force pilot casually confirms he bombed the guerrilla camp that the search operation inadvertently revealed. Hal is horrified: The humanitarian search for T. may have led to a military strike on people who could have been Mayan refugees.
The next morning, walking to retrieve T., Hal is stabbed by a boy who steals his wallet. He collapses on the sidewalk, bleeding heavily, too weak to call for help. A stray black dog nuzzles his face. Hal finds comfort in the animal, thinking of T.'s three-legged dog and concluding that dogs represent "the ambient love of the world" (250). His thoughts turn to Casey. He wants to tell her that when she was born, he was born too, that she made him necessary. He reflects that it is not one man who suffers for the world but the whole world, the poor in their billions, who suffer so a fraction can live in comfort. Casey showed him the world was full of hurt things, but his own world shrank to contain only the one that mattered, and he forgot all the rest. The novel ends with Hal alone on the concrete, gravely wounded and possibly dying, addressing Casey in his mind: "For you we give up the world" (253).