Dwight is the hard-working, loyal, soft-spoken captain of the American nuclear submarine. He knows how to lead a crew and he does it well. He also realizes that his job carries obligations and that he must fulfill them, even in these trying and strange circumstances. Dwight does his work with a sense of who he is and what his role is in the world. His competence, responsibility, and integrity spill over into his personal life. These characteristics are especially apparent in his relationship with Moira. Dwight is honest with Moira about his loyalty to his wife, and he maintains that integrity until the very end.
Although Dwight is a practical, rational man, he clings to the belief—though perhaps aware of his delusion—that his family is still alive and well in America. Dwight simply does not have the imagination to be able to grasp that the American people, his family included, no longer exist. Dwight is also very obedient, and in some instances his obedience seems extreme. When asked how he would respond if he had been in the position to stop dropping the bombs during the nuclear war, Dwight admits that, although he would like to think he would have negotiated, he probably would have continued the bombing just as the world's real leaders did. Dwight also refuses to break the rules to allow Moira onto the submarine when he scuttles it. His inflexibility may maintain his integrity, but it also leaves Moira to die alone.
Moira is a lively, flirtatious twenty-four-year old woman who turns to alcohol as a relief from the despair that she will never be able to marry, have a family, travel, or fulfill any of her other dreams. Whenever the morbid reality of the situation becomes too overpowering, she escapes to drink and dance. Moira finds life tedious because has nothing else to do but help on her parent's farm. In the beginning of the novel, Mary Holmes enlists Moira to keep Dwight entertained and distracted during his brief visit. Moira does succeed in this regard, as she manages to bring fun and excitement to Dwight's last months. In turn, Dwight helps Moira find some peace with their inevitable fate.
More than any other character, Moira uses her last months to transform and better herself. She begins to drink less and attend church more often. When she complains about her boredom and her longing to have something to do, Dwight encourages her to take secretarial classes like she planned to do before the war started. Although Moira knows it is crazy and useless to take the classes, she does and finds joy in her learning and accomplishments. While she understands that Dwight will remain loyal to his wife until the end, she cannot help herself from falling in love with him. As the months progress, Moira reveals a more tender and generous side to her tough-talking, party-girl personality. When she finds out that Dwight wants to find a pogo stick for his daughter, Helen, Moira makes an admirable effort to find one for him. Moira dies by herself in her car at a cliff overlooking the ocean, her lonely death the final image of the novel.
Peter is a Lieutenant Commander in the Royal Australian Navy who is assigned to serve as a liaison officer aboard the American nuclear submarine commanded by Dwight Towers. Peter is a hard-working military man who loves the sea and his job. Whenever he is not working, he is helping his wife Mary take care of their baby daughter, Jennifer, and their house. Peter is strong enough to face the fact that he might have to kill his daughter when radiation sickness sets in, but he still clings to hope and plans his garden for the next ten years. Peter admits he does not have the imagination to believe the world is really going to end. Shute is concerned that we, as readers, also lack the ability to imagine this vivid, unfathomable outcome; if we do not believe a nuclear war will happen, we will not act to stop the arms buildup. At the end of the novel, Peter advocates that more education and information in newspapers might have prevented the war. Peter is an extraordinarily ordinary person, intentional on Shute's part so that we might relate to him easily. The more we can relate to the characters, the more likely we will take seriously the threat of nuclear war and do what we can to prevent it.
Mary, Peter's wife, is a housewife who finds comfort and pride in creating a beautiful home and taking care of her family. She spends most of the time raising baby Jennifer and thinking of ways to improve their garden. More than any other character, Mary resists accepting that her safe, controllable world is coming to an end. Peter is critical of Mary for "living in a dream world," but we might sympathize with the new mother's refusal to believe her family will die. While others calmly deal with the calamity, Mary sobs and screams against the situation that forces her to consider the prospect of euthanizing her own child. Mary is an archetype of a young mother, and is supposed to be someone to whom we can easily relate. She intentionally disregards the news and newspapers because they are always full of bad news. Mary's insistence on ignoring what is going on in the world is a warning to us: like Mary, we can continue to tune out world events, but like Mary, we might eventually find ourselves in a situation in which such simply become impossible to ignore any longer.
John is a young scientist working for CSIRO (the Commonwealth Scientific and Industrial Research Organization). More than any other character, he faces the reality of the situation and uses the last few months to realize and fulfill his dreams. Indeed, John truly lives for the first time only when he is in the shadow of death. Despite his fears, he goes on the submarine, and he takes even bigger risks when he races his Ferrari. Near the end of the novel, however, Osborne reaches his goal of winning the Australian Grand Prix. He also becomes a member of the Pastoral Club, an exclusive club he has always wanted to join. At the end of the novel, it is almost a shock to find out that John has a mother who is still alive. Although he is related to Moira and Douglas, John seems to be very much alone and not deeply connected to other people—in some sense, a misfit trying to be cool. John's death is lonely, but the way he wants it to be, in his Ferrari.
John's reaction to the war symbolizes the way the scientific community responds to the disaster. While scientists should be horrified about the war they have helped to create, they continue to objectively conduct experiments. John declares he will have fun discovering the effects of radiation poisoning, not considering the moral and ethical implications of having fun at the expense of millions of lives. It is this scientific objectivity and detachment that has made it possible for researchers to create the bombs in the first place. In his position as scientist and engineer, John is very much Shute's alter ego. From his own life experience as an engineer, Shute understands the minds of scientists and engineers who create weapons of war.