Dee is a seventeen-year-old girl who finds herself falsely convicted of murdering her stepsister, Monica. Haunted by a traumatic childhood kidnapping that left her with severe trust issues, she brings a fierce determination and rebellious attitude to her wrongful imprisonment. She refuses to accept the helpless role assigned to her by the island's authorities, intent instead on proving her innocence and exposing the corrupt system that sent her there.

Nyles is a tall, blonde British pre-medical student who serves as the unofficial orientation guide for new arrivals on Alcatraz 2.0. He claims to possess diplomatic immunity while his conviction for his parents' murder is on appeal, granting him a degree of safety from the executioners. He projects a calm, breezy demeanor that helps offset the island's daily horrors and quickly becomes a stabilizing force for Dee.

Griselda is a skilled hacker convicted of murdering her boyfriend and roommate. She embraces an edgy, provocative persona on camera to maintain high viewer ratings, knowing that popularity extends her lifespan on the island. She initially presents herself as prickly, cynical, and exclusively focused on self-preservation.

Ethan is a muscular former personal trainer who was convicted of killing a client in what he insists was self-defense. He approaches the terrifying reality of Alcatraz 2.0 with an exuberant, puppy-like energy, treating survival scenarios like scenes from his favorite 1980s action movies. He maintains his physical fitness rigorously to stay prepared for attacks.

The Postman is a wealthy, anonymous television mogul who struck a deal with the United States president to privatize capital punishment. He controls every aspect of Alcatraz 2.0 from a remote computer, manipulating the inmates' lives, arranging their relationships, and orchestrating their televised executions to maximize app viewership and profit.

Blair is an Asian woman with blue-streaked hair who formerly lived in San Francisco with her wife. As the manager of the island's ice cream shop, she takes it upon herself to teach Dee the unwritten rules of surviving Alcatraz 2.0. She is openly defiant of the island's administration and refuses to submit to their degrading expectations.

Mara is Dee's shy, reclusive, redheaded neighbor on Alcatraz 2.0. She keeps largely to herself after facing sexual harassment at her island job. She reveals herself to be deeply analytical, having extensively studied the habits, dialects, and real identities of the island's serial killers prior to her incarceration.

Kimmi is a blonde, blue-eyed teenager who abducted eleven-year-old Dee and held her captive in a white, windowless room. Obsessed with forcing Dee to be her sister, she utilized psychological manipulation and threats of violence to enforce compliance. She was eventually sent to a psychiatric hospital after Dee escaped.

Monica is Dee's murdered stepsister. Prior to her death, she was a good-natured fashion enthusiast who enthusiastically followed the Postman app, holding a particular fascination for the executioner Gucci Hangman. She was found strangled in her bedroom with a heart carved into her shoulder.

Dee's father is a fiercely protective parent who uprooted his life to shield his daughter after her childhood trauma, officially changing their identities. Following Dee's wrongful conviction, he works diligently with attorneys on the outside to appeal her case and secure her freedom.

Prince Slycer is one of the state-sponsored serial killers employed on Alcatraz 2.0. Known collectively as "Painiacs," these killers adopt specific personas to entertain viewers. Slycer embraces a dark fairy-tale aesthetic, hunting victims dressed as princesses through elaborate mazes.

Gucci Hangman is a flamboyant executioner on Alcatraz 2.0 who adopts an extravagant drag persona. He utilizes high-end designer scarves as garrotes and is known for leaving specific, carved marks on the bodies of his victims.

Dr. Farooq is a corrupt psychiatrist whose testimony sent Dee, Griselda, and Ethan to Alcatraz 2.0. She uses manipulative hypnosis techniques to implant false memories and record coerced confessions, operating as a key component in the system that supplies innocent teenagers to the island.

Rodrigo is a greasy-haired inmate representing the older, genuinely guilty population on Alcatraz 2.0. A convicted sexual predator, he routinely harasses the female inmates and serves as a constant threat in the island's public spaces.