The film begins with on-screen captions explaining that a medical breakthrough in 1952 has permitted the human lifespan to be extended beyond 100 years. It is narrated by 28-year-old Kathy H (Carey Mulligan) as she reminisces about her childhood at a boarding school called Hailsham, as well as her adult life after leaving the school. The first act of the film depicts the young Kathy, along with her friends Tommy (Andrew Garfield) and Ruth (Keira Knightley), spending their childhood at Hailsham in the late 1970s.The students are encouraged to create artwork, and their best work gets into The Gallery run by a mysterious woman known only as Madame (Nathalie Richard). One day, a new teacher, Miss Lucy (Sally Hawkins) quietly informs the students of their fate; they are destined to be organ donors and will die, or "complete", in their early adulthood. Shortly afterward she is sacked by the headmistress, Miss Emily (Charlotte Rampling) for sharing this revelation with the children. As time passes, Kathy falls in love with Tommy, but Ruth and Tommy begin a relationship and stay together throughout the rest of their time at Hailsham.In the second act, Kathy, Ruth and Tommy, now teenagers, are rehoused in cottages on a farm in 1985. They are permitted to leave the grounds on day trips but are resigned to their eventual fate. At the farm, they meet former pupils of schools similar to theirs, and it is revealed that they are all clones. They also hear rumors of the possibility of "deferral" - a temporary reprieve from organ donation for donors who are in love and can prove it. Tommy becomes convinced that The Gallery at Hailsham was intended to look into their souls and that artwork sent to The Gallery will be able to confirm true love where it is present. The relationship between Tommy and Ruth becomes sexual, and jealousy causes Kathy and Ruth to break their friendship. The lonely Kathy leaves and becomes a "carer" - a clone who is given a temporary reprieve from donation as a reward for supporting and comforting donors as they are made to give up their organs. Tommy and Ruth's relationship ends.In the third and final act, 10 years later, Kathy is still working as a carer, and has watched many clones gradually die as their organs are harvested. Kathy, who has not seen Ruth or Tommy since the farm, discovers Ruth, frail after two donations. They find Tommy, who is also weakened by his donations, and drive to the sea. There, Ruth admits that she did not love Tommy, and only seduced him because she was afraid to be alone. She is consumed with guilt and has been searching for a way to help Tommy and Kathy. She believes that the rumors of "deferral" are true, and has found the address of the gallery owner, Madame from Hailsham, who she thinks may grant deferrals to couples in love. Ruth dies on the operating table shortly afterward.Kathy and Tommy finally begin a relationship. Tommy explains to Kathy that he has been creating art in the hope that it will aid deferral. He and Kathy drive to visit Madame, who lives with the headmistress of Hailsham. The two teachers tell them that there is no such thing as deferral, and that Tommy's artworks will not help him. They explain that the purpose of The Gallery was not to look into their souls but to investigate whether the "all but human" clones even have souls at all; Hailsham was the last place to consider the ethical implications of the donor scheme. As they take in the news on their return journey, Tommy breaks down in an explosion of rage and frustration and Kathy and he cling to each other in grief. The film ends with Tommy dying on the operating table.Kathy is left alone, waiting for her donations which will begin in a month. Contemplating the ruins of her childhood, she asks in voice-over whether her fate is really any different from the people who will receive her organs: after all, "we all complete".