Nina is a 38-year-old librarian living in Northampton who keeps her 68-year-old mother confined to the upper floor of their home. Though she works a steady job and interacts with library patrons, she harbors intense resentment and strongly desires a child of her own. She experiences sudden bursts of intense emotion accompanied by distorted vision, seeing the world in black and red. Her current life involves rigid routines, such as preparing specific meals for Maggie while strictly controlling her access to the outside world.

Maggie is a 68-year-old former medical clinic receptionist currently living as a prisoner in her own home. Restricted by an ankle chain, she spends her time observing the neighborhood from an upstairs window and secretly searching for items to aid her escape. She maintains a fiercely protective attitude toward her daughter despite her captivity. She justifies her past decisions, believing she acted correctly to shield Nina from distress.

Bobby is a sensitive young reporter who contacts Nina through social media. Adopted as an infant by a wealthy family, he is currently searching for details about his origins. He cautiously initiates a friendship with Nina, visiting her house and engaging in frequent text conversations. He values his independence and personal space, stepping back when people become overly demanding.

Jon is a charismatic local musician in his twenties who leads the band The Hunters during the 1990s timeline. He actively pursues relationships with teenage girls, viewing their youth as an asset rather than a boundary. He leverages his local fame to manipulate his followers while living in a chaotic apartment. He dismisses the concerns of parents and adults who question his behavior.

Alistair is Maggie's husband and Nina's father during the 1990s timeline. He shares an affectionate bond with his teenage daughter, frequently calling her his "only girl" and building a custom wooden memory box for her keepsakes. His sudden absence from the family household deeply damages the relationship between his wife and daughter.

Elsie is an elderly neighborhood resident who shares a long-standing friendship with Maggie prior to Maggie's disappearance. She receives assistance from her adult daughter Barbara for transportation and daily tasks. She observes the Simmonds household from over the garden fence and quietly questions the official story regarding Maggie's sudden move to a care facility.

Sally Ann is an 18-year-old pregnant young woman during the earlier timeline. She officially dates Jon Hunter and shares an apartment with him. She proudly identifies him as her boyfriend in music magazines, completely unaware of the dangerous web of jealousy surrounding their relationship.

Jane is a wealthy woman who adopted Bobby as an infant. She raised him in a supportive environment and maintains a strong, loving connection with him in his adulthood. She remains oblivious to the complex circumstances surrounding his biological origins.

Claire is a social worker assigned to evaluate Nina's application to become an adoptive parent. She is professional and thorough, relying on reference calls to make her final determinations regarding placements.

Barbara is Elsie's adult daughter. She visits the neighborhood to assist her elderly mother with transportation and daily care, ensuring her physical safety.

Louise is a neighbor who is currently pregnant after experiencing a previous miscarriage. Her presence in the neighborhood reminds Nina and Maggie of their own past traumas regarding pregnancy.

Noah is Bobby's romantic partner. He cares for Bobby and shares a steady relationship with him, but finds himself targeted by Nina's intrusive behavior when she demands more of Bobby's time.

Saffron is Nina's teenage friend from the 1990s. She spends time with Nina during her rebellious phase, though Nina often abandons her at events to pursue the band members backstage.

Dr. Kelly is Nina's current physician who prescribes her medication and recommends counseling. She inadvertently helps Nina discover major inconsistencies in her past medical history.

Dr. King is a physician from the medical clinic where Maggie worked decades ago. Maggie frequently cites his diagnoses to justify administering various medications to teenage Nina at home.

Jennifer is Maggie's sister and a retired nurse. She does not actively appear in the neighborhood, but Nina frequently uses her as a convenient cover story, telling neighbors that Maggie moved in with Jennifer after developing dementia.