Kathy is a reflective, observant young woman raised in an isolated English boarding school for cloned children. She works as a carer, tending to organ donors across the country while finding comfort in her memories of the past. She is naturally introverted and empathetic, often acting as a peacemaker, though she wrestles with her own quiet desires and her complex feelings for her closest friends.

Tommy is an earnest, somewhat naive student at Hailsham who struggles with severe anger issues during his youth. His violent outbursts are largely triggered by other students bullying him over his lack of artistic creativity. With the help of the school staff, he slowly learns to manage his emotions, though he remains anxious about his place in the school's peculiar culture.

Ruth is Kathy's assertive and highly insecure best friend at Hailsham. She desperately seeks approval and attention, often inventing elaborate games or lying to make herself appear more important. Despite her occasional vindictiveness and manipulative behavior, she possesses a deep-seated fear of being left out or abandoned.

Madame is a stern, middle-aged woman who regularly visits Hailsham to collect the students' best artworks. She maintains a cold detachment from the students and visibly suppresses shudders when near them. The students view her with a mixture of awe and fear, wondering why she treats them as though they are dangerous.

Miss Emily is the fearsome and intimidating head guardian at the Hailsham boarding school. Older than the other staff members, she commands immense respect from the students for her strict demeanor. She operates the school with a firm belief in its sheltering methods, striving to provide the children with an ordered, safe environment.

Miss Lucy is a guardian at Hailsham who struggles with the school's policy of obscuring the truth from the students. She is guilt-ridden and honest, quietly believing the children deserve to fully understand the reality of their futures as organ donors. She takes a special interest in helping students cope with their anxieties.

Chrissie is an older resident at the Cottages who is fascinated by the students from Hailsham, believing them to hold special privileges. She is keenly interested in rumors about deferrals from organ donations for couples who are in love. She subtly manipulates situations to extract information from the younger students.

Rodney is a veteran resident at the Cottages who follows Chrissie's lead in interacting with the Hailsham graduates. He organizes a trip to Norfolk under the pretense of finding the woman Ruth was cloned from. He is generally agreeable but clearly driven by his desire to find a way out of his scheduled donations.

Miss Geraldine is a beloved, gentle guardian at Hailsham who is adored by the younger children. She inspires such intense devotion that the students form secret clubs to protect her from imaginary threats. Her well-meaning praise occasionally causes unintended social consequences for the students.

Laura is a fellow Hailsham graduate who transitions into the difficult role of a carer. She serves as a point of connection for Kathy in the outside world, sharing news and rumors about their mutual acquaintances from school. She embodies the exhaustion common to their profession.

Harry is a quiet student at Hailsham whom Kathy briefly considers starting a physical relationship with. He is discreet and does not gossip about Kathy's intentions, earning her respect. He fades into the background of the school as the students grow older.