Peter Holmes, an Australian naval officer, wakes up happy because today he will meet with the Navy Department in Melbourne, the southernmost large city in the world. He expects the meeting to lead to a new appointment and his first work in seven months. He has not worked since the "short, bewildering war" ended.
The nuclear war started in the Northern Hemisphere and lasted for thirty-nine days. Peter was on a Navy ship during the war, but he is now back home in Falmouth, a suburb of Melbourne, with his wife, Mary, and his baby daughter, Jennifer. Since the war ended, there is no more gasoline for cars, so Peter rides his bicycle to a farm to get milk. He then takes his bicycle over to the train station, where the parking lot is full of horses instead of cars.
Peter takes the train to Melbourne and goes to the offices of the Navy Department. He meets with an admiral who assigns him to the position of liaison officer aboard the U.S.S. Scorpion, an American nuclear submarine. Peter has already met Dwight Towers, the submarine captain, who is a pleasant, affable man.
When the war started, Dwight received orders from the U.S. Navy to take the Scorpion to Manila. Four days later, his instruments detected radioactive dust above the empty sea. He was unable to establish contact with any American radio station or ship. When Dwight established contact with Australia, he took the sub south. On his way down, he came across an American cruiser. For the first time, he learned about the war and its origin—newspapers and radio stations had ceased operations during the war, so many people were left without knowledge of how or why everything started. Dwight learned that Albania initiated an Arab-Israeli war, which led to a Russia-NATO war, which led to a Russo-Chinese war. Atomic bombs fell all over the Northern Hemisphere.
Peter learns he will be posted to the Scorpion for a year. During that time, the submarine will take one short and one long cruise. Peter is troubled by the thought of leaving Mary alone with the baby, especially since radioactive dust—traveling southward on global wind currents—is expected to reach Melbourne soon. Nevertheless, Peter accepts the position, knowing Mary would be mad if he did not.
Peter meets Dwight and invites the American captain to his home. Dwight accepts because he does not want to be stuck at the docks all weekend with only his thoughts and memories of his life in America. Peter returns home to tell his wife about his new assignment and the invitation he extended to Dwight. Mary gets upset that Peter invited the American to visit, remarking how painful it is for people from the Northern Hemisphere to go into people's homes and be reminded of what they have lost in the war. To distract Dwight from painful memories while he visits, Mary decides to have a party and invites her friend Moira Davidson. Moira is not particularly thrilled about meeting a widower from the Northern Hemisphere, but she accepts.
Moira greets Dwight at the train station in her horse and buggy, and she takes him for a drink. Moira uses flirtation, conversation, and alcohol in an attempt to distract Dwight from his past. The two then go to the local sailing club and participate in a sailing race. During the race, Moira purposely capsizes the boat and loses her bra, playfully accusing Dwight of being responsible for both mishaps.
After the party that night, Dwight and Moira talk. She is very drunk. He tells her that there is a mysterious radio transmission still coming from the Seattle area, although is it doubtful anyone is alive there. The radiation is spreading south steadily. Moira angrily asks why the radiation has to come to Australia since they were uninvolved in the war and all the bombs were dropped in the Northern Hemisphere, thousands of miles away. Dwight remarks that nothing can stop the wind. He explains how the equatorial trade winds slow down the radiation but do not completely stop it from drifting. Moira admits she is not afraid of dying, but she is angry about everything she will never get to do, like traveling and having a family. At the end of the conversation, drunk from another whiskey, Moira sobs uncontrollably.
The innocence and domesticity of the opening scene understates the enormity of the events that have shaken Peter Holmes's world. War is not even mentioned until the third page, and even then it is merely described as a "short war." The subtle narrative style of the opening pages sets the tone for the entire novel. Rather than shock the reader with hysterical dialogue and gruesome details, Shute makes the horrific war ordinary enough to seem possible. He concentrates on domestic scenes because the victims of this war will die in their homes, not on battlefields. The warring armies are anonymous, but the civilian characters are real and detailed. Like many of Shute's novels, On the Beach is about ordinary people caught up in extraordinary events.
At first, it may appear shocking that Peter would leave his wife and daughter to for a voyage when radiation sickness will soon end all of their lives. But Peter has not yet accepted the fact he will die: he is still planning for his future career, and he knows that his wife has the same outlook. Furthermore, Peter truly loves his work, and, like many of the characters in the novel, he would like to spend his last days working. Work is both a salvation and a distraction from thinking about the hopeless times in which the characters live. Because Moira does not have much to keep her busy, she spends her day drinking, and ends up depressed. When Dwight suggests to her that the time left might be a "period of grace," he is foreshadowing Moira's transformation into a sober and gentle person who finds dignity in work during the last months of her life.
Moira's sobbing episode at the end of the chapter is one of the few emotional scenes in the book, and Moira's only tearful bout. The stoicism and calmness of the characters is surprising, considering they are living through that last days of humanity on earth. Their reactions are a reflection of the novel's epigraph—the world will end "not with a bang but a whimper." This quotation, which comes from T.S. Eliot's poem "The Hollow Men," tells us how the story will end even before the novel opens. As the novel progresses, we see the characters continue to fill their time with their daily routines, taking little time to cry out against their fate and reaffirm the dignity of humanity.
At the time On the Beach was written, during the Cold War, many people believed a potential conflict would only involve major Northern nations such as the United States and the Soviet Union. More remote nations, such as Australia, lived with the illusion that radiation from a nuclear war in the Northern Hemisphere would not drift into the Southern Hemisphere. Shute wants to correct this misassumption, so he has Dwight explain that the winds will carry the radiation to Australia—it is impossible to avoid the wind. Dwight and Moira agree that it is unfair to suffer from the conflicts of people thousands of miles away; however, fair or not, they must accept that all people on the planet share one fate. Environmentalists embrace On the Beach because of its message that humans all share the same planet and that an environmental disaster in one part of the world can affect everyone, everywhere.