On the Beach recap

After a nuclear war destroys the Northern Hemisphere, Australia waits for radioactive fallout to move south. American submarine commander Dwight Towers, Australian liaison officer Peter Holmes, scientist John Osborne, and Moira Davidson try to maintain useful work and ordinary relationships while their remaining time contracts. Scorpion sails north to test a theory that radiation may be declining and to investigate a radio signal from Seattle, but the measurements offer no reprieve and the signal is only an accidental mechanical transmission. Back in Melbourne, John races his Ferrari, Peter prepares Mary for their family's death, and Moira falls in love with Dwight while respecting his devotion to his lost family. As radiation sickness arrives, the government distributes drugs for quick deaths. John dies with his car; Peter, Mary, and their baby die together; and Dwight takes Scorpion to sea to sink with his crew. Moira watches the submarine leave and prepares to take her own dose.

A nuclear war has destroyed the nations of the Northern Hemisphere. Australia was not attacked, but radioactive air is steadily moving south, and the country's leaders expect it to become lethal within months. Peter Holmes, a young Australian naval officer living near Melbourne with his wife Mary and their baby Jennifer, is recalled to duty. He is assigned to the American nuclear submarine USS Scorpion, one of the few surviving vessels, under Commander Dwight Towers. The work gives Peter purpose but also brings him closer to the official forecasts that Mary prefers not to discuss. Dwight behaves as though his wife and children still live in Connecticut, buying gifts for them and preserving the habits of a husband temporarily away. Peter introduces him to Moira Davidson, a lively young woman whose drinking and parties are her way of confronting the same future. Their companionship begins cautiously.

Scorpion is prepared for a northern voyage to measure radiation and test a scientific suggestion that weather patterns may be clearing some areas sooner than predicted. John Osborne, a scientist serving with the navy, joins the mission. Away from duty he has acquired a Ferrari and devotes himself to preparing it for a final season of motor racing, an activity that now seems no less rational than saving for a future that will not arrive. Moira grows attached to Dwight. He enjoys her company but remains emotionally faithful to Sharon, the wife he knows cannot realistically be alive. Moira chooses not to challenge that loyalty and begins drinking less. Peter and Mary continue planning their garden and household while Peter tries to make her face the practical question of protecting Jennifer when radiation sickness reaches them.

Scorpion travels through contaminated northern waters. Its readings disprove the hopeful interpretation of the radiation data: the deadly material is not disappearing quickly enough to save Australia. The crew then investigates an erratic Morse transmission coming from the Seattle region. Lieutenant Sunderstrom goes ashore in protective gear and finds no survivor. The transmission is being produced accidentally by damaged equipment disturbed by chance movement, not by a human operator. Near San Francisco, crewman Ralph Swain leaves the submarine to spend his remaining time in the place where his family lived, accepting the fatal exposure. The vessel turns south with no rescue, refuge, or surviving community to report. The journey removes the last plausible hope that the catastrophe may leave a habitable northern pocket.

After Scorpion returns to Australia, private plans replace national ones. The government issues instructions and medication so that people can avoid the prolonged final stages of radiation sickness. Peter obtains doses for himself, Mary, and Jennifer, but Mary recoils when he explains that they may have to administer the baby's dose before taking their own. Dwight spends time with Moira and considers what duty requires of him when operations can no longer continue. He still buys presents for his family and speaks of returning home, a discipline Moira recognizes as inseparable from him. John enters the increasingly dangerous Grand Prix in his Ferrari. With normal rules losing force and several drivers killed, he wins the race and gains the achievement on which he has fixed his remaining ambition.

Radiation sickness reaches Melbourne. John Osborne closes himself in the garage with his Ferrari and uses its exhaust to die on his own terms. Peter becomes ill and returns home. When Jennifer also shows symptoms, Mary finally accepts that delaying would only leave the child to suffer after her parents were incapacitated. Peter and Mary use the government medication and ensure that Jennifer dies with them. Moira asks Dwight to remain ashore with her, but he will not abandon either his crew or the responsibilities he associates with his lost American home. He takes Scorpion out for a final voyage so that the submarine and its company can be sunk at sea. Moira follows the vessel's progress from the coast until it disappears, then prepares to take her own dose. No corrective scientific effect or surviving northern population has been found; the last southern communities meet the same end as the rest of humanity.

The radiation reaches southern Australia and sickness becomes widespread. John Osborne seals himself in the garage with his Ferrari and dies beside the machine that gave purpose to his final months. Peter takes the government-issued drug after helping Mary understand that they must also end baby Jennifer's life rather than leave her to die alone. Dwight refuses Moira's plea to remain in Australia: he considers it his duty to stay with his crew and take Scorpion out to sea. Moira drives to the coast and watches the submarine depart on its final voyage, understanding that Dwight and the crew will sink their vessel and die together. She then turns to the pills she has brought with her. The mysterious American radio signal has proved mechanical rather than human, and no refuge has been found; the novel closes with the last surviving communities accepting that the fallout will extinguish them as well.