Sara is a 38-year-old museum archivist specializing in postcolonial Africa. She is detained at the Madison facility without a hearing because a corporate algorithm flagged her dreams and lifestyle choices as a risk to society. Inside the facility, she attempts to drive her algorithm score down by obeying strict, ever-changing rules while separated from her husband and young twins. She keeps a detailed handwritten dream journal to maintain her sanity and preserve her connection to her historical career.

Elias is Sara's practical husband, who struggles to manage household debt and childcare alone outside the retention center. Mohsin and Mona are their young twin toddlers, who grow increasingly distant from their mother during her prolonged absence. The family unit represents the normal life Sara is desperate to return to, though Elias's insistence that she simply follow the rules creates emotional distance between them.

Hinton is the senior guard and attendant at the Madison retention facility. He utilizes his position of authority to enforce arbitrary rules, issue petty infractions, and extend the retention times of the women under his watch. He has a burn scar on his neck and takes specific pleasure in targeting those who show intelligence or resistance.

The Madison Chief Retention Officer is an unnamed executive for the private contractor Safe-X. He primarily works offsite and views the retention center strictly as a source of profit, prioritizing free labor and cost-cutting measures over the health and safety of the retainees. He frequently obscures his face with a surgical mask during his rare visits to the facility.

Introduced to the other women as Eisley Richardson, a confident fitness trainer, she is secretly Julie Renstrom, an employee for the Dreamsaver corporation. She enters the facility under the guise of a retainee to conduct corporate research on targeted subconscious advertising. She lives a comfortable life outside the facility but struggles with a failing marriage and distance from her children.

Toya is an insurance claims adjuster currently held at Madison. She deals with chronic health issues that the facility frequently ignores to save money. Down-to-earth and stubbornly loyal, she provides a grounded perspective on the realities of their detention and shares grueling laundry room shifts with Sara.

Emily is a firefighter and aspiring comic book artist who shares a room with Sara at the retention center. She spends her free time drawing a comic about a non-superhero protagonist trying to manage ordinary burdens. She is observant, kind, and quick to recognize physical dangers like smoke and fire.

Victoria is a young retainee at Madison who uses her appearance and cunning to survive the strict rules of the facility. She possesses a natural insubordination and a willingness to take significant personal risks to disrupt the constant surveillance forced upon the women.

Lucy is an older accounting clerk who worked for a real estate company prior to her detention. She faces accusations of identity fraud tied to a customer lawsuit against her company. She is practical and no-nonsense, though her secretive nature makes her a target for suspicion among the other women.

Marcela is a young musician and guitarist for an indie band. She is detained at Madison after a dispute with neighbors escalated into property damage and traffic violations. She projects an image of rebellion but often directs her frustration at other retainees rather than the system holding her.

Abdo is Sara's attorney, tasked with working within a legal system that relies on proprietary algorithms he cannot access. He consistently advises Sara to follow all rules and remain compliant, prioritizing a smooth bureaucratic process over fighting the systemic injustices of the retention center.

Williams is an attendant at Madison who assists Hinton in enforcing control over the retainees. He frequently abuses his position to sexually harass the women and issues official write-ups when they reject his advances.

Jackson is the attendant in charge of work assignments at the Madison facility. He is responsible for ensuring the retainees fulfill the labor quotas required by Safe-X's corporate contracts and attempts to use bribes and threats to maintain productivity.

Segura is an officer for the Risk Assessment Administration. He questions Sara at the airport about her travel funding, social media presence, and sleep data, ultimately deciding to place her under a retention order based on her algorithm score.

Zach is Sara's cousin who has an old criminal record based on false charges. His legal history negatively affects Sara's algorithmic risk score. He writes to her in detention, attempting to offer help while dealing with the fallout of his own ruined reputation.

Saïd is Sara's younger brother who drowned in a pool during a childhood game of hide-and-seek. His death fractured their family and remains a profound source of trauma and guilt for Sara.

Peter is Julie's husband. He is generally unsupportive of her workplace frustrations and creates emotional distance in their marriage by prioritizing his own comfort and ignoring her complaints.

McClure is an engineer at Dreamsaver who competes directly with Julie for a promotion. He works on a social feature to allow people to record and share their dreams, representing the company's push toward total loss of privacy.

Alice is Toya's roommate at the Madison facility. She is deeply concerned about her algorithm score and hesitant to participate in any actions that might jeopardize her chances of early release.

Sara's unnamed father is an immigrant who changed the family surname to avoid suspicion. He withdrew from family life after the death of his son but remains a cautious, conservative voice urging Sara not to make trouble.