Elizabeth is a young woman who works as a telemarketer and serves as the sole caretaker for her identical twin. She carries the heavy burden of managing their shared childhood trauma, constantly monitoring her sister's severe mental health episodes. She attempts to establish an independent life by secretly dating a coworker, but feels intense guilt over seeking happiness outside their insular apartment.

Emily is Elizabeth's identical twin sister who suffers from extreme depression and agoraphobia. She rarely leaves their shared apartment and frequently engages in self-harm, such as scratching her leg with a thumbtack or using a carving kit, as a method of coping with the lingering pain of their abusive childhood. She relies entirely on her sister for emotional regulation and reacts aggressively to any perceived outside threats to their routine.

Thomas is a kind, straightforward Christian studying to become a youth pastor. He works at the same telemarketing office as Elizabeth and has been dating her for nearly a year. He grows increasingly frustrated by her refusal to let him visit her home or meet her twin sister, pushing for a more integrated relationship.

The biological mother of the twins is characterized by her extreme neglect and cruelty. She allowed dangerous individuals to abuse her daughters, creating the terrifying environment that forced the girls to rely exclusively on each other for physical survival.

Lisa is a clinical therapist who treated the twins during their childhood following their rescue from an abusive environment. She provides a safe, familiar presence and offers professional guidance when Elizabeth feels overwhelmed by her caretaking responsibilities.

Dalila is the twins' adoptive mother. She provided them with a safe home and structure after their early childhood trauma. Despite her initial desire to rescue the girls, she struggles with heartbreak and distance due to their persistent psychological walls and intense codependency.

Bob is the adoptive father of the twins. He works alongside his wife to provide a secure environment for the girls, but experiences significant difficulty managing their intense rages and inability to trust adult caregivers.

Rose is a young patient in the hospital's psychiatric ward who suffers from severe anorexia and body dysmorphia. She quickly befriends Elizabeth, offering practical advice on how to work around the strict ward rules and manipulate the medical staff for an early discharge.

Dr. Larson is a psychiatrist assigned to oversee Elizabeth's case following a severe crisis. He asks direct, clinical questions and challenges his patients' narratives, attempting to break through their psychological defenses.

Polly is a staff member on the locked psychiatric ward. She enforces the facility's strict protocols, such as mandatory supervision, while managing the daily movements of the patients.

Mark is a psychologist who runs the daily group therapy sessions for the unit. He attempts to de-escalate volatile situations when patients spiral into paranoia or violent outbursts.

Rick is a patient in the psychiatric unit who struggles with paranoia, serving as part of the ward's challenging daily environment.

Doris is a highly volatile patient on the psychiatric ward. Her sudden, violent outbursts require physical restraint by security, contributing to the chaotic and frightening atmosphere of the locked unit.

Felicia is a nursing aide on the psychiatric unit. She assists patients with their evening routines, administers sleep aids, and manages their personal belongings.

Dr. Heimer is a psychiatrist on the hospital's treatment team. She bluntly restates difficult facts during evaluations, often triggering strong emotional reactions from the individuals under review.

Shelly is a confrontational patient on the psychiatric ward. She frequently disrupts sessions with explosive anger and demands explanations from new arrivals, forcing other patients to intervene.

James is a staff member at the psychiatric facility. His primary duty is to provide continuous, direct observation for patients who require heightened security protocols.

Teresa is an occupational therapist at the psychiatric hospital. She encourages patients to engage in creative exercises, like building boxes to hold their worries, as a method of processing their emotions.