Alex is a 17-year-old high school student attending the prestigious St. Vincent de Paul Academy on scholarship. Hardworking and ambitious, he aims to attend Georgetown University and eventually become the first president of Puerto Rican descent. When a massive asteroid strikes the moon and his parents go missing, Alex steps into the role of household provider. He relies on his intelligence and strict adherence to rules to protect his younger sisters in a rapidly deteriorating city.

Briana is the 14-year-old middle child of the Morales family. She possesses a quiet, timid nature but shows immense dedication to her household chores. Devoutly Catholic, she relies heavily on religious ceremonies, prayer, and her rosary beads to manage her fears about the disaster. She respects Alex's temporary position as head of the family and acts as a peacemaker between her brothers and sister.

Julie is the 12-year-old youngest child of the Morales family, attending Holy Angels Catholic school. Accustomed to the role of the baby of the family, she initially responds to the disaster with dramatic demands and frustration. Despite her initial whining, she deeply loves her family and slowly adjusts to the new reality of their situation, eventually finding purpose in school activities like tending a vegetable garden.

Kevin is a cynical, street-smart student at St. Vincent de Paul Academy. Unlike the deeply religious Alex or the wealthy Chris Flynn, Kevin relies on practicality to survive. His father owns a trucking company that profits from the disaster, and Kevin uses his gritty awareness of the city to secure supplies, forming an unexpected bond with Alex.

Father Franco is the compassionate priest at St. Margaret's Church. He serves as a critical source of information and spiritual comfort for the surrounding neighborhood. He manages the community bulletin boards, tracks missing persons, and offers personal counsel to terrified parishioners, doing everything in his power to support the Morales children through their uncertainty.

Father Francis Patrick Xavier Mulrooney is the severe, imposing new headmaster of St. Vincent de Paul Academy. Coming out of retirement, he teaches Latin and advanced theology with a strict, unbending voice of authority. He insists that the natural disasters are no excuse for skipping education, maintaining rigorous expectations for his students despite the collapsing city.

Mami is the hardworking mother of the Morales children. She is employed as an operating room assistant at a hospital in Queens. Before the asteroid hits, she manages the household chores with her daughters and maintains a tradition of lighting candles for her children's birthdays at St. Margaret's Church.

Papi is the father of the Morales children and works as a manager for their New York City apartment building. When the asteroid hits, he is visiting the coastal village of Milagro del Mar in Puerto Rico for his mother's funeral. He is a loving father who previously set clear expectations for his children, which Alex strives to uphold in his absence.

Carlos is the oldest Morales sibling. He serves as a marine stationed in California. Being military personnel, he is immediately deployed when the global disaster begins, leaving his younger siblings to handle the situation in New York on their own.

Uncle Jimmy is the children's uncle, who operates a local bodega. Following the initial shock of the asteroid, he quickly mobilizes to secure his store from looters. He allows Alex and Julie to take a modest supply of food home in exchange for their labor.

Aunt Lorraine is Uncle Jimmy's wife and the aunt of the Morales children. Pregnant with her fourth child, she becomes highly anxious and worried as the reality of the natural disasters sets in.

Chris is the wealthy junior class president at St. Vincent de Paul Academy. He maintains an ongoing academic rivalry with Alex. Unlike the scholarship students, Chris belongs to a privileged class that can easily evacuate New York for safer locations like South Carolina.

Robert Flynn is Chris's wealthy father. He stays behind in New York to manage business affairs while sending his family away to South Carolina. He notices Alex's strong work ethic and extends a quiet offer of emergency assistance.

Joey owns the pizza parlor where Alex works. As the disaster begins, he struggles with short staffing and quickly realizes his business will likely fail as the city shuts down. He ensures Alex receives his outstanding wages before closing shop.

Greg Dunlap is a tenant in the same apartment building as the Morales family. He stops to chat with Alex just before the power grid fails and eventually decides to evacuate New York for Vermont.