This is the story of Kathy and her friends Ruth and Tommy. All three of them grew up together in a place called Hailsham, where they are raised for the purpose of organ harvesting later on in their lives. They are kept creative, educated and healthy to best suit their futures as organ "donors." There are a lot of things that aren't explained to these kids, like where their work goes or why they are made for what they are, and some of them spend the book trying to figure these out.
Kathy is the main character of the book, and she's a bit of a passive person in my opinion. She isn't proactive, she lets things happen to her. But she is a very curious person, and in this, she sees some odd things that are happening around her. Miss Lucy, the guardian, is a prime example of this: she often says and does odd things around the kids. She tells them things she shouldn't, like how she used to smoke, and Kathy once caught her scribbling on a page vigorously. Kathy takes note of this behavior and puts some pieces together to figure out what's happening in their lives.
Ruth is a very aggressive, assertive person and someone others look up to. She mostly just cares about herself from what the readers see, and she is manipulative in all of her relationships. She doesn't really notice the strange things going on around her because she's too wrapped up in drama and fights.
Theme: Human Mortality
Tommy is a very dynamic character when it comes to his personality and behavior, because in the beginning of the book he's super immature, very easily irritable, and throws a lot of fits. Throughout the book, though, he is able to calm himself down and manage his emotions better, and forms good relationships with people like Kathy. He does notice some of the oddities throughout the book because he is usually the one to firsthand experience Miss Lucy's antics. He and Kathy confide in each other about these and notice a pattern.
The motif of family is carried throughout the book by Kathy's relationships with her peers, guardians, and even the possibles they look for from time to time. The guardians act like parent figures, as they raise them and teach them about life, and are there for emotional support and to answer questions. They are also similar to parents in that some subjects of conversation with them are taboo and they will not hesitate to punish the children if they do something wrong. Peers are kind of like siblings because she spends all her time with them, even while they're sleeping, and they have to learn to behave and interact with each other well. Kathy and Ruth look up to their possibles to hopefully find similarities or explanations of their own behavior in them, as you might with older family
The book dips into the topic of human mortality through a metaphor: the organ donations these children go through and how they prepare for them can be related to real life in the way we prepare for death. On page 36 of the book, Kathy speaks about how guardians constantly prepare them for their organ donations and they give presentations and have discussions and show videos and all of those things, but what's going to happen to the children never really sinks in and they don't really understand until they witness/experience it for themselves to understand the impact. This is similar to real life in that when a child's pet or family member dies, the parents/guardians try their best to explain but it doesn't completely explain the concept to the child brain.