Jane is a 55-year-old divorcée living alone with her four dogs in a crumbling ancestral estate. Feeling she lacks purpose, she discovers a lost West Highland terrier named Hugo in the woods, which sparks an amateur investigation into a missing teenage girl. She is a resilient, observant woman who uses her empathetic nature to extract information from strangers, driven by a desire to confront shadows from her own past.

Stuart is a scruffy man in his fifties who lives off a small inheritance. Seeking an easy life, he moves into Thornwood after meeting Jessamine at a pub, only to find himself entangled in an intensely restrictive household. He functions as the primary caregiver and cook for the family, offering a gentle presence in an otherwise hostile environment.

Jessamine is a troubled former child actress who struggles with severe alcoholism and emotional volatility. She lives at Thornwood with her mother and daughter, rarely leaving the house and relying on Stuart to manage her daily needs. Her erratic moods dictate the atmosphere of the home, swinging from needy vulnerability to outright cruelty.

Daisy is a sullen, withdrawn teenager raised in extreme seclusion at Thornwood. Following a strange police visit during a pandemic lockdown, she becomes obsessed with investigating her family's past and her own identity. She drops out of school and isolates herself in her room, writing online stories before eventually running away to uncover the truth.

Allen is the late patriarch of the Black family who worked as a department head at John Lewis. He cultivated an image of absolute middle-class respectability, presenting himself as a handy, doting husband. In private, he wielded absolute control over his household and preyed on vulnerable young women he hired as au pairs.

Annie is the fastidious matriarch of Thornwood and Allen's widow. She is obsessed with maintaining social propriety and a veneer of normality, insisting on formal domestic rituals. Her dedication to appearances makes her entirely complicit in the abuses that occur within her home, as she prioritizes secrecy over the safety of others.

Jasper is the estranged son of the Black family who ran away to join a circus. Profoundly affected by his childhood at Thornwood, he adopts an alter ego named "Patch the Clown" to process his trauma and distance himself from his family. He lives a solitary life in a caravan, maintaining his unsettling clown persona even while off duty.

Dexter is Jane's adult stepson who lives near the Vale of Health. He eagerly joins Jane's amateur investigation, offering practical ideas and acting as a sounding board. He is highly supportive of his stepmother, encouraging her to formalize her detective work and sell her burdensome country estate.

Claire is a bright, friendly young woman with a degree in music technology. On a summer day in 2005, she takes a shortcut across Hampstead Heath and accidentally stumbles into the Black family's orbit. Her trusting nature makes her vulnerable to Allen's predatory charm.

Tony is Jane's second ex-husband. He lives in a comfortable London property and maintains a surprisingly warm, encouraging relationship with Jane, offering her a place to stay while she looks into the mystery of the missing girl.

Tobias is a retired security consultant who previously worked for Tony. He utilizes his professional connections to dig up old police records regarding Thornwood, providing Jane with crucial evidence about cold cases.

Dr. Twist is a London-based psychotherapist specializing in trauma processing. He previously treated Jasper Black, and though bound by confidentiality, his guarded responses confirm Jane's suspicions about Jasper's state of mind.

Harvey is the married founder of a clothing company who maintained an affair with Jessamine. He eventually cuts ties with her, prompting Stuart to investigate the true nature of Harvey's connection to the family.

George is a teenage boy who attended primary school with Daisy. He provides Jane with a current physical description of Daisy and shares local rumors about the strange atmosphere surrounding her family's home.