- The decent, soft-spoken captain of the American nuclear submarine. Although Dwight is considered a practical, rational man, he continues to believe—or at least pretend to believe—that his family is still alive in nuclear-war- ravaged America. Work is Dwight's salvation, and he continues to work hard whether he has to or not. He refuses to break rules, and remains loyal to the Navy and his wife until the end of his life.
in-depth analysis of Dwight Towers.
- A hard-drinking, tough-talking flirtatious single young woman from Australia. Moira prefers to dance and drink than face the reality that the approaching radiation means she will never have the opportunity to fulfill her dreams. Even though she knows Dwight will never be disloyal to his wife, Moira becomes his good friend, bringing life and excitement to Dwight's last months. In turn, Dwight's influence helps Moira find some peace with their inevitable fate.
in-depth analysis of Moira Davidson.
- A lieutenant commander in the Royal Australian Navy. Peter, like Dwight, is a real Navy man who longs to go to the sea even if it means leaving his wife, Mary, and baby daughter, Jennifer, during their last few months alive. When Holmes is not working, his time is consumed with domestic matters, such as gardening and shopping. He does his best to take care of his family. On the whole, he is very much an ordinary man, written that way intentionally so that we might easily relate to him.
in-depth analysis of Peter Holmes.
- Peter Holmes's wife. Mary lives for the comfort and domesticity of her family. Up until the last moments, she refuses to accept that her world is coming to an end. Some view her as weak and suffering delusions, while others sympathize with her as a protective, loving new mother.
in-depth analysis of Mary Holmes.
- Peter and Mary Holmes's baby daughter. Jennifer is a constant source of worry for her mother, especially when her father returns from a voyage during which one of the submarine crew comes down with the measles.
- A scientist with CSIRO, the Commonwealth Scientific and Industrial Research Organization. More than any other character, John faces the reality of his impending death and uses his last few months to fulfill his dreams. Traveling on the submarine and racing his Ferrari give him the chance to break from his mundane lifestyle. Attracted to wealth and exclusivity, Osborne joins the fancy and formal Pastoral Club. Often cynical, he is described by Moira as "dippy." He gets nervous easily, but tries—usually successfully—to hide his fears. As a scientist and engineer, John is the character with whom Shute could most readily identify. For this reason, he describes, but never mocks, John's love for machines.
in-depth analysis of John Osborne.
- Moira's father. Mr. Davidson is a cattle rancher who cares for his farm and his animals until the very end. He is a hard-working man who loves his land.
- Moira's mother. Mrs. Davidson still wishes her daughter will get married and have children despite the fact that she only has a few months left.
- A former Lieutenant General in the Australian navy. The elderly Douglas plans to spend the last few months of his life drinking all the vintage port left in the wine cellars of the Pastoral Club. His goal is to finish all the port before he dies from the radiation.
- The submarine's radio and electric officer who goes on shore to investigate the mysterious radio signals coming from Santa Maria Island. Sunderstrom enjoys the Saturday Evening Post
and has great admiration for well-made machines.
- A young crew member on the submarine who jumps ship just off his home town in Washington state so that he can spend his last days there. After visiting his house and seeing the bodies of his family, Yeoman Swain spend his final days fishing.
- Dwight Towers's wife. Sharon does not appear as a character in the novel, as she was killed during the war in America, but Dwight constantly thinks of her and remains loyal to her to the end.
- Dwight's nine-year old son, who was also killed in the war. Dwight still dreams of teaching Junior to fish.
- Dwight's five-year old daughter, who was killed in the war. Dwight scours the toy stores in Melbourne in search of a pogo stick to buy for Helen.
- A dairy farmer who provides milk and cream to the Holmes family. Mr. Paul asks Peter to help make a trailer with motorcycle wheels so that he can pull his wife into town, wanting to help her enjoy her last days.
- A conscientious doctor who treats Dwight when he falls ill after his long sea voyage. A few weeks before the radiation comes to Melbourne, Dr. Fletcher performs surgery on a woman in order to enable her to live a few more years.
- The director of the State Fisheries and Game Department. Sykes is initially reluctant to move up the starting date of the fishing season, but he ultimately gives into pressure and opens the waters for fishing.
- The Prime Minister of Australia. Mr. Ritchie explains the submarine's mission to the crew.
- A scientist who comes up with the controversial theory that precipitation in the Northern Hemisphere will clean the air of radiation and keep it from reaching Australia. This theory is referred to as the Jorgensen effect.