Jules is a woman burdened by past trauma and estranged from her older sister. She returns to her childhood hometown of Beckford to handle Nel's affairs and take custody of her teenage niece, Lena. She suffers from a deep-seated fear of the local Drowning Pool and struggles with fragmented memories of a painful event from her youth.

Lena is Nel's fifteen-year-old daughter. She is grieving both her mother and her recently deceased best friend, Katie, who died in the same river. Sullen and fiercely independent, she strongly mistrusts Jules and the police, insisting she knows more about what happened to her mother than the authorities do.

DI Sean Townsend is a respected local Detective Inspector leading the investigation into Nel's death alongside DS Erin Morgan. He carries personal childhood trauma related to the Drowning Pool, as his mother Lauren died there when he was young. As he interviews the grieving townspeople, he struggles with his own fragmented memories and the mounting pressure of the case.

Erin is a Detective Sergeant who recently transferred to Beckford from London following a workplace issue. She brings an objective, outsider's perspective to the town's history of drownings. She is diligent and observant, quickly noticing the strange dynamics among the locals and her partner's uncharacteristic behavior.

Nel is Jules's sister and Lena's mother, whose recent death in the Drowning Pool sets the story in motion. Prior to her death, she was researching a book about the history of "troublesome women" who died in the local water. Her aggressive pursuit of other people's pasts made her deeply unpopular with many of the town's residents.

Louise is a grieving mother struggling to cope with her teenage daughter Katie's recent suicide in the Drowning Pool. She intensely dislikes Nel Abbott, blaming her entirely for Katie's death. Her overwhelming grief frequently manifests as anger toward those she feels failed her daughter.

Josh is Katie's twelve-year-old brother. Sensitive and anxious, he struggles quietly with the tension in his grieving family. He observes the town's events carefully and feels burdened by information he is keeping secret about his sister's final days.

Mark is a teacher at the local school who taught both Lena and Katie. Following the recent tragedies in Beckford, he frequently swims alone and desperately wants to leave town to start over. He spoke with Nel shortly before her death, leaving him anxious about what information she might have left behind.

Patrick is Sean's father and a retired police officer living in a converted barn behind his original house, where his son now resides. He holds traditional, rigid views about women's behavior and frequently complains about the town's residents. He spends much of his time observing his daughter-in-law, Helen, and experiencing early symptoms of memory loss.

Helen is Sean's wife and the head teacher at the local school Lena attends. Pale and frequently anxious, she prefers the quiet company of her father-in-law over dealing with the town's escalating drama. She is deeply unsettled by the recent deaths in Beckford and privately worries about her husband's state of mind.

Nickie is viewed by Beckford residents as either a psychic or a local nuisance. She walks with a cane and sports purple streaks in her hair. She claims descent from the town's historical accused witches and frequently converses with the spirit of her dead sister, Jeannie, while observing the town's drama from the fringes.

Katie is Louise's deceased daughter and was Lena's closest friend. Her recent suicide in the Drowning Pool paralyzed the town and left her family devastated. Before her death, she collected rocks and walked into the water, an act that continues to haunt those she left behind.

Robbie is Nel's high school boyfriend who still resides in the area. His unexpected appearance at Nel's funeral triggers a visceral reaction in Jules. He remains a looming figure from the Abbott sisters' youth, tied to a traumatic event that fractured their relationship years ago.

Libby is a historical figure from the 1600s who serves as the first subject in Nel's manuscript about the Drowning Pool. Accused of witchcraft after a scandal involving a married man, her drowning established the town's long history of violently punishing women who step outside societal norms.

Lauren is Sean's late mother and Patrick's deceased wife. She died in the Drowning Pool in 1983 under circumstances that Nel was aggressively investigating for her book. Her death remains a source of deep, unresolved trauma for her son.