Henry is a 42-year-old founding partner of a software design company. He grew up in a deeply abusive environment in a house on Cheyne Walk, which has left him with an obsessive personality and an intense fixation on order and cleanliness. He harbors a long-standing infatuation with his childhood companion, Phineas, and has undergone several cosmetic procedures to resemble him.

Lucy is Henry's 40-year-old sister who carries herself with natural elegance despite years of poverty and housing insecurity. She makes a living by busking with her violin and desperately wants a permanent, safe home for her children. Having survived severe childhood trauma in the Cheyne Walk house, she acts as a fiercely protective mother while keeping secrets about her recent past in France.

Rachel is a 32-year-old jewelry designer living in London. She struggles to make her business profitable and relies on her supportive father for financial backing, making her feel insecure when comparing herself to younger peers. Lonely and seeking connection, she enters a whirlwind romance with a charming man she meets in Martha's Vineyard.

Samuel is a dedicated, clearheaded detective inspector in London. Without a wife or children, he pours his entire focus into his police work and becomes personally invested in his cases. He possesses an excellent ability to read body language and spot lies, making him a formidable investigator when looking into long-buried secrets.

Michael is a wealthy, charismatic man in his forties who claims to own properties in Martha's Vineyard, a ski chalet, and a house in Antibes, France. He projects an image of worldly success and charm, which he uses to sweep women off their feet. However, his sophisticated exterior masks a controlling, volatile, and dangerous personality.

Libby is a 25-year-old woman with blond hair, blue eyes, and freckles. She inherited a large, overgrown house on Cheyne Walk where she was found abandoned as a baby 25 years earlier. Despite selling the property for millions of pounds, she lives modestly in a flat and acts evasive when the police ask questions about the house's history.

Phineas, known as Phin, is a man who grew up alongside Henry and Lucy in the Cheyne Walk house. He works as a guide in Africa but abruptly leaves his post to travel to Chicago. He struggles with his identity and the traumatic memories of his youth, choosing to isolate himself from the people he knew as a child.

Birdie, also known as Bridget, was a violin player in the pop band Original Version in the 1980s. She moved into the Cheyne Walk house after filming a music video there and brought a con artist into the home. She is remembered by survivors of the house as a deeply manipulative and cruel woman who controlled the children living there.

Justin is a former member of the band Original Version who lived at the Cheyne Walk house and tended its garden. Now working as a gardener and living in a camper van, he has long hair, tattoos, and piercings. He carries immense guilt over leaving the children behind in the abusive household and has struggled with addiction for years.

Marco is Lucy and Michael's teenage son. After spending years facing housing insecurity and occasionally sleeping on the streets, he deeply values the stability of living in his uncle Henry's apartment. He is technologically savvy and actively helps his mother track down leads online.

Brian is Rachel's highly supportive and encouraging father. He provides the financial backing for her jewelry business and offers a safe haven for her during personal crises. Despite his steady demeanor, he hides his own financial troubles from his daughter to protect her.

Kris is a bisexual man who runs motorbike tours in Chicago. He is friendly, open, and remains concerned about his ex-boyfriend Phin's whereabouts. He inadvertently becomes a source of information for multiple people trying to track Phin down.