Set two decades after an environmental catastrophe renders Earth's surface uninhabitable, the story centers on a wealthy family—Mother, Father, and their 20-year-old Son—who have isolated themselves in a luxurious bunker deep within a converted salt mine, along with a few other individuals: Friend, one of Mother's oldest friends; Butler, an aging queer man who serves the others; and Doctor, who provides them with medication and keeps track of safety precautions and procedures. The Son, having spent his entire life underground, yearns to experience the outside world he has never seen and build scale models of historical events and places. The family follows a regular schedule, including safety emergency drills, fitness at an indoor pool, regular duties to keep the bunker and their small outpost running, and managing a collection of fine art Mother had brought with them. The family also decorates the bunker to evoke the changing seasons. The Mother wants everything to appear perfect, and obsesses over the details of the bunker's decor and layout. The Son is helping the Father write his memoir, while taking creative liberties around the Father's former work as an oil tycoon and describing his work as "energy sector" and describing in detail his philanthropy. The Friend describes to the Son how her son was sick with cancer and would not have survived in the bunker. The Son struggles with loneliness and longing to experience the world. The group eventually finds a Girl unconscious in the mines and bring her in to question her about how she found them. The Girl describes the uninhabitable surface and says that her family died when they tried to cross a river, and she is alone, later reflecting on her trauma. They decide to cast her back out onto the surface, but the Girl escapes and runs through the bunker, evading them until the Son pleads for them to let her stay. The Girl struggles to adapt to life in the bunker. Mother is suspicious of the Girl, and voices her concerns to the Father while also trying to teach the Girl about their life and trying to investigate her motives. The Mother tries to be intimate with the Father, who is surprised by her actions. The Girl and the Son slowly bond. The Son confesses to his parents that he is developing feelings for the Girl, and they argue about the nature of love and the Son's naïveté. The Son gifts the Girl with a watch, but she appears hesitant. The Girl argues with the Son about his scale models of the outside world when he tries to justify the brutality of the
first transcontinental railroad. The Mother and Friend both struggle with sleeplessness and nightmares, which the Doctor downplays and prescribes them sleeping pills. During a writing session, the Son tries to learn more about their lives before and learn more about how his Father met Mother. The Butler and the Father describe love and longing, and the Son writes a flowery and embellished version of events where the Father met the Mother, which he later mimics back to the Mother. Time moves on and they enter the winter. The family celebrates New Year's Eve with a program of skits and elaborate homemade costumes of animals, where the Butler and Father perform a soft shoe tap dance. During the New Year's Eve dinner, the Girl appeals to the Mother about leaving the rest of humanity behind, arguing with her about what guilt they must feel before the Father stops the conversation. Mother struggles with survivor's guilt, and after arguing with the Father who tells her that she chose this life as well, the Mother justifies their actions of leaving her family behind. The Father continues to justify his actions while writing the book with the Son, and later tries to convince the Girl of his innocence, saying that all of the other corporations were worse than he was and he at least "cared". The Father reflects on his actions, his own mortality and age, and continues to justify how they contributed to the end. Eventually, the Son argues with the Father about why they left everyone else behind, and the Friend confesses that her son did not die from cancer but struggled with addiction, and she chose to leave him to come to the bunker. She later gets more sleeping pills from the Doctor and overdoses. The Son is distraught when they discover her body and argues with the Girl, telling her that it is her fault her family is dead. Some time in the future, the Son and the Girl have a baby together, and the family gathers to celebrate the Girl's birthday, taking a family photo. The Girl and the Mother both ponder the future. ==Cast==