Peter is an officer in the Royal Australian Navy who serves as the liaison officer on the USS Scorpion. He is a resourceful officer who takes practical steps to maintain a sense of order despite the impending global disaster. Driven by a deep sense of duty to both his profession and his family, he balances military obligations with keeping his household comfortable.

Dwight is an officer in the United States Navy and the commander of the USS Scorpion, an American submarine now stationed in Australia. He is a disciplined military leader who strictly adheres to protocol. He relies heavily on memories of his family in Connecticut, frequently talking about them as if they are still alive as a coping mechanism for his immense grief.

Mary is a young housewife who finds peace in domesticity. She cares for her infant daughter and actively plans for the future by ordering flower bulbs for her garden. She completely compartmentalizes the looming threat of radiation fallout. Instead, she focuses exclusively on the safety and routine of her immediate home environment.

Moira is a young woman whose family owns a large sheep and cattle farm. Feeling aimless in the post-war situation, she spends her time drinking heavily and attending parties. She possesses a sharp wit and a cynical outlook, though her growing connection with Dwight encourages her to participate more actively in farm work.

John is a scientist hired by the military to track radiation levels across the ocean. He approaches the apocalypse with cold factual analysis combined with a sudden thirst for adrenaline. Rather than lamenting his fate, he purchases a Ferrari and spends his free time working on the vehicle to prepare for the Australian Grand Prix.

Jennifer is Peter and Mary's infant daughter. She is entirely dependent on her parents and serves as the primary focus of Mary's domestic life and Peter's protective instincts.

Sharon is Dwight's wife, who resided in Mystic, Connecticut, with their two children before the war. Dwight continually buys gifts for her and speaks of their marriage, keeping her memory alive as he navigates his duties in Australia.

Junior is Dwight's young son. Dwight frequently imagines buying him a fishing rod and bringing it back to America for him.

Helen is Dwight's daughter. Dwight searches the shops of Melbourne for a pogo stick to give to her.

Mr. Davidson is Moira's father and a wealthy landowner. He maintains his property with diligence, continually completing farm projects and preparing his land for the future despite the approaching fallout.

Mrs. Davidson is Moira's mother. She disapproves of her daughter's heavy drinking but refrains from arguing given the short amount of time they have left to live.

Sir Douglas is a former lieutenant general and John's great-uncle. He chooses to spend his final months at an English gentlemen's club, steadily depleting their extensive stores of alcohol rather than worrying about the future.

Yeoman Swain is a crew member on Dwight's submarine. He is originally from Edmonds, Washington, and his intense connection to his hometown deeply affects his behavior when the ship arrives in American waters.

Lieutenant Sunderstrom is an expert in radio communications aboard the USS Scorpion. He is tasked with going ashore in a protective suit to investigate the source of a sporadic radio signal near Puget Sound.

Allan is the director of the Game Department. He initially opposes the idea of opening the trout fishing season early due to conservation rules, a position that creates friction with those wanting to enjoy their final days.