Scott is an 11-year-old boy living in a New York City suburb in 1962. Caught between childhood innocence and the looming adult anxieties of the Cold War, he tries to balance typical pre-teen concerns while processing the escalating political tensions. He serves as an empathetic observer of the chaotic world around him, questioning the societal norms and prejudices he witnesses.

A pragmatic and deeply anxious man who constructs a fallout shelter beneath his family's playroom in response to the escalating Cold War. His proactive approach to the nuclear threat strains his marriage but ultimately places him in a difficult leadership position when neighbors force their way into the shelter. He tries to manage limited resources while keeping the group from turning on one another.

Ronnie is Scott's assertive and rebellious friend, dealing with the onset of puberty and a desire to appear tough. He uses bravado and boundary-pushing behavior to mask his deeper insecurities regarding the impending threat of nuclear war. Once trapped in the shelter, his aggressive facade frequently crumbles.

A contentious neighbor who forces his way into the fallout shelter during the attack. He quickly establishes himself as a divisive presence, allowing his fear and desperation to manifest as hostility. He frequently suggests discarding basic ethics to ensure his own survival and weaponizes his prejudices against vulnerable members of the group.

Scott's mother is deeply skeptical of her husband's intense preparations for nuclear war, preferring to distance herself emotionally from the existential threat. Her profound anxiety over the crisis causes her to become increasingly withdrawn in the months leading up to the attack. During the rush to the shelter, she suffers a severe head injury that leaves her unresponsive.

Scott's younger brother embodies the innocence of childhood. He frequently relies on Scott for comfort and understanding as he struggles to comprehend the terrifying realities of both the looming war and the claustrophobic fallout shelter.

The Black maid employed by Scott's family, who ends up trapped in the shelter alongside them. Despite enduring overt racism from some of the neighbors and carrying immense anxiety about her own children on the outside, she steps up to provide vital first-aid care.

Ronnie's wealthy father, who maintains a relaxed and confident demeanor in the pre-attack timeline. However, the prolonged confinement and hopelessness of the fallout shelter severely impact his mental state, causing him to behave erratically and succumb to panic.

Ronnie's mother, accustomed to an affluent suburban lifestyle. In the shelter, she struggles significantly with the lack of amenities, openly criticizing the preparations and battling the degradation of the cramped, unhygienic conditions.

Mr. McGovern's daughter and the object of Scott's adolescent crush. She endures the trauma of the shelter while coping with the horrifying reality that her mother did not make it inside before the door was sealed.

Scott's sixth-grade teacher serves as a calm voice of reason in the pre-attack timeline. He challenges his students to think critically about complex social issues, delivering objective lessons on racism, civil rights, stereotyping, and the geopolitical realities of the Cold War.

A neighborhood friend of Scott and Ronnie who participates in their pre-teen antics before the attack. He shares their underlying anxieties about the escalating global conflict but is not among those who make it into the shelter.

Paula's twin brother has a physical disability and uses a wheelchair. His presence subtly illustrates the exclusionary attitudes of the neighborhood children during the pre-attack timeline.

A neighbor of Scott's family who owns the cheesecake that Ronnie insists on stealing. Her judgment causes Scott immense embarrassment when he is forced to apologize to her.

One of the neighbors who manages to secure a spot in the overcrowded fallout shelter, assisting in the chaotic moments following the blast.

A classmate of Scott and Ronnie who frequently engages in disruptive behavior and challenges the authority of their new teacher.

A neighborhood boy known by a distinct nickname who participates in the children's anxious preparations and games leading up to the crisis.