Kyle is a 16-year-old student at Stuyvesant High School who lives in Brooklyn Heights. Following the September 11 attacks, he takes on the role of temporary caretaker for his uncle and a traumatized girl he rescues from the bridge. He tries to maintain stability and control in his household while struggling to communicate with his stranded mother and his first-responder father.

Hannah is a teenage ballet student who survives the immediate aftermath of the attacks but suffers from trauma-induced fugue amnesia. Kyle finds her wandering the bridge and brings her to his home for safety. Without memory of her name, past, or family, she exhibits a gentle demeanor and relies heavily on Kyle's protection as she slowly processes fragments of her identity.

Matt is Kyle's uncle and a former NYPD Emergency Services Unit officer who sustained a severe spinal cord injury in a motorcycle collision. Now reliant on a wheelchair and requiring constant assistance for daily tasks, he lives with Kyle's family. He possesses a brilliant mind and previously trained for national memory championships.

Tom is Kyle's father and a dedicated NYPD officer serving on the Joint Terrorist Task Force. Following the attacks on the World Trade Center, he works tirelessly at Ground Zero as a first responder. His intense dedication to his duty creates a protective but sometimes emotionally guarded dynamic with his family.

Marcus is Kyle's best friend who lives with his adoptive parents in uptown Manhattan. Originally from Uganda, he was adopted as a young child after his birth parents were killed in a civil war. He provides Kyle with a sobering perspective on tragedy, survival, and the reality of living in a locked-down city.

Alyse is Kyle's mother. She was scheduled to fly back to New York from Los Angeles on the morning of September 11. Grounded on the West Coast due to the nationwide flight stoppage, she relies on brief, patchy phone calls to ensure her family remains safe in Brooklyn.

Kerri is Kyle's younger sister, an aspiring actress with a love for Disney and boy bands. She is stuck in California when all commercial flights are grounded, leaving her bedroom empty for Hannah to temporarily occupy.

Paul is Kyle's uncle and an active NYPD officer. He traditionally criticizes Kyle's academic choices, preferring a more conventional tough-guy approach to life, but the citywide crisis reveals his underlying care and concern for his family's safety.

Karina is Uncle Matt's professional caretaker who assists with his daily medical and physical needs. When the city shuts down, her absence forces Kyle to take on more responsibilities, though she eventually returns to support the family with homemade Polish food.

Madame Yvette is a fortune teller operating a small shop. She possesses an eerie ability to perceive past tragedies and future recoveries. Her blunt assessments of her clients' lifelines cause significant distress.

David Marconi is a high-profile lawyer who works in One World Trade Center. He defends a controversial client in a prominent criminal case, a professional choice that causes immense strain in his personal life.

Danielle Marconi is the late wife of David Marconi and a former creative director of the New City Ballet. She passed away from ovarian cancer months before the story begins, leaving a profound void in her family.

Bangor is a high school friend of Kyle and Marcus. He is directly impacted by the World Trade Center collapse, as his uncle worked in the buildings during the attacks.

Jenny is a classmate and friend of Kyle. Her father was likely in the Towers during the attacks, representing the widespread personal losses among Kyle's peer group.