Mark is a volunteer sweeper on team Omega tasked with clearing stragglers from Zone One, the heavily fortified area formerly known as Manhattan. Before the virus outbreak, he worked in Customer Relationship Management, a job he considers perfectly suited to his lifelong mediocrity. In the post-apocalyptic world, however, he discovers a latent talent for survival that transforms his view of himself. He suffers from PASD (Post-Apocalyptic Stress Disorder), which causes frequent flashbacks to his past and his time on the run.

Gary is a civilian sweeper operating within team Omega alongside Mark and Kaitlyn. He maintains a deliberately unkempt, grimy appearance that he defends as a holdover from his previous work at his father's garage, resisting military pressure to clean up. He treats the infected with aggressive disdain and dark humor, often making a game out of their violent duties by instigating rounds of "Name that Bloodstain!"

Kaitlyn is the third member of team Omega, bringing a practical, level-headed approach to their clearing operations in Zone One. As a former sorority girl and student council secretary, her privileged background contrasts sharply with the grim reality of her current environment. Despite the horrors she has witnessed on the road to Fort Wonton, she maintains an earnest belief in the reconstruction efforts and the potential to restore human civilization.

The Lieutenant serves as the highest-ranking official at Fort Wonton, overseeing both the military personnel and civilian volunteers. He acts as the primary liaison between the ground teams in Zone One and the central command in Buffalo. Eccentric and unconventional, he approaches his leadership duties with a philosophical mindset, occasionally expressing vocal sympathy for the harmless infected known as "stragglers."

Ms. Macy is a public-relations official dispatched from the central military headquarters in Buffalo. She tours Zone One in clean clothing and painted nails, projecting an image completely disconnected from the brutal daily realities of the sweepers. Her primary objective is to gather positive reports on the reconstruction progress to maintain morale and prepare for an upcoming global summit.

Bozeman functions as the top military clerk stationed at Fort Wonton. He manages logistical information and acts as a coordinating figure within the base's operations. He works closely with the visiting officials from Buffalo and remains tuned in to the broader strategic movements concerning the zone's reconstruction.

Mim (Miriam Cohen Levy) is a survivor Mark meets during his early days on the run. They form a practical and romantic bond while barricaded inside a toy store during the cold winter months. She carries the trauma of losing her children to the virus and imparts crucial survival philosophies to Mark, particularly the importance of always remaining ready to flee at a moment's notice.

Fabio operates as a military clerk and serves as the second-in-command to the Lieutenant at Fort Wonton. He remains primarily inside the base managing administrative duties and assignments while the sweeper teams patrol the city.

Quiet Storm is a fellow civilian volunteer who previously worked alongside Mark. While clearing wreckage on the congested I-95 highway, Quiet Storm focuses on the eccentric task of rearranging abandoned cars to spell out readable messages for overhead aircraft.

Richie is part of the North Corridor operation team tasked with clearing highway wreckage. He works closely with Mark and Quiet Storm during their assignment to restore a clear pathway between Washington D.C. and Boston.

Uncle Lloyd is Mark's relative who lived in a New York City apartment before the virus outbreak. Mark's childhood memories of visiting Lloyd's home shape his early appreciation for the scale, ambition, and constant destruction inherent to the city's progress.

Mark's mother appears in his traumatic flashbacks to the beginning of the apocalypse. She is a resident of Long Island whom Mark discovers fully infected when he returns home from a trip to Atlantic City.

Mark's father is a resident of Long Island who falls victim to the virus during the initial outbreak on the Last Night. He appears in Mark's dark, frequently suppressed memories of the apocalypse's beginning.