Theo is a 42-year-old forensic psychotherapist living in London. He takes a new position at The Grove psychiatric hospital specifically to treat the high-profile patient Alicia Berenson. He struggles with a history of mental health issues and a traumatic childhood, seeking validation through his work. When he accidentally discovers his wife's infidelity, his personal life spirals into obsessive jealousy, standing in sharp contrast to his professional determination to help his silent patient.

Alicia is a 33-year-old successful painter committed to The Grove psychiatric hospital after shooting her husband, Gabriel. She completely stops speaking following the murder, communicating her state of mind only through a haunting self-portrait titled "Alcestis." Before the tragedy, she kept a personal diary that documented her creative struggles, her deep love for her husband, and her growing paranoia regarding a stalker outside her home.

Kathy is an American-born actress in her late thirties living in London. She presents a bold, confident, and theatrical personality that deeply attracts her husband, Theo, who views her as a savior from his dark past. Her secret infidelity shatters Theo's idealized view of their marriage and drives him to stalk her in an attempt to uncover her lover's identity.

Gabriel is a 44-year-old fashion photographer and the murdered husband of Alicia Berenson. In Alicia's diary, he appears as a stabilizing force who encourages her art, though he outright dismisses her fears about being stalked. He projects an image of a highly successful, confident artist who enjoys the spotlight.

Max is a solicitor and Gabriel's adopted brother. He handles Gabriel's estate and serves as Alicia's primary legal contact after the murder. Max expresses intense dislike for Alicia and paints her as violent and unstable to investigators, though his interactions with her suggest a more complicated dynamic filled with resentment.

Vernon and Eva are Alicia's deceased parents, whose tragic lives cast a long shadow over her mental stability. Eva dies in a car crash with young Alicia in the passenger seat, an event Alicia suspects was intentional. Vernon later dies by suicide in the family home's attic. Their combined emotional neglect deeply traumatizes Alicia and shapes her artistic expression.

Paul is Alicia's cousin, who grew up alongside her after her mother's death. He still lives in his childhood home, caring for his domineering mother, Lydia. He struggles with gambling debts and alcohol use. He lives the trapped, dependent existence that Theo desperately wanted to escape.

Lydia is Alicia's belligerent aunt, who took her in after Eva's death. She harbors deep resentment toward her niece, describing her as ungrateful and difficult. Lydia struggles with deteriorating mental health and acts tyrannically toward both Alicia and her own son, Paul.

Professor Diomedes is the clinical director of The Grove and a prominent figure in forensic psychiatry. He testified at Alicia's trial, ensuring she was sent to a psychiatric unit rather than prison. He serves as an authoritative, paternal figure to Theo, giving him a strict six-week deadline to get Alicia to talk.

Yuri is the head psychiatric nurse at The Grove, originally from Latvia. He presents a relaxed, friendly demeanor that contrasts with the strict hospital environment. While he initially appears helpful and warns Theo against getting too close to Alicia, his interactions with patients hint at a willingness to bend institutional rules.

Elif is a highly aggressive and unpredictable patient at The Grove who was institutionalized for murdering her mother and sister. She frequently targets Alicia, seeking to provoke the silent woman through cruel remarks and physical altercations.

Tanya is Max Berenson's wife and assistant. She exhibits a fearful, nervous demeanor around her controlling husband. Despite her timidity, she takes a quiet risk by secretly directing Theo to speak with Paul Rose to learn the truth about Alicia's past.

Christian is a psychiatrist at The Grove who previously worked with Theo at another facility. The two men share a mutual dislike. Christian favors heavy medication for Alicia and strongly opposes Theo's attempts to lower her dosage or engage her in talk therapy.

Jean-Felix manages the art gallery that represents Alicia and has known her since their art school days. He is fiercely protective of her artistic legacy but often views her more as a valuable commodity than a personal friend. He provides Theo with crucial access to Alicia's artwork.

Ruth is Theo's former psychotherapist, who helped him manage his suicidal ideation during his university years. She serves as a maternal, grounding figure in his life. Theo seeks her guidance when his marriage begins to fall apart, relying on her straightforward, empathetic advice.

Theo's parents are the source of his profound childhood trauma. His father was physically and emotionally abusive, constantly berating Theo, while his mother was severely depressed and failed to protect her son. Their influence lingers over Theo, driving his desire to fix others through psychotherapy.

Indira is a psychiatrist at The Grove who radiates a calm, motherly presence. Unlike Christian and Stephanie, she supports Theo's unconventional methods to reach Alicia and believes in the healing power of empathy and non-verbal communication.

Barbie is Alicia and Gabriel's former neighbor. She frequently visits The Grove under the guise of being Alicia's close confidante, though she mostly talks about herself. Barbie was one of the few people Alicia told about her stalker before the murder.

Stephanie is the newly appointed manager of The Grove, brought in by an oversight trust to fix the institution's financial issues. She represents the bureaucratic threat to the hospital's existence, prioritizing safety protocols and operational efficiency over experimental therapy.