Although the story reveals what the life of the a clone is like from beginning to end, the real drama is not about the structure of their lives, but within it. A rumor begins to circulate at The Cottages-- where Kathy and her friends Ruth and Tommy are transferred after school to await training-- that students from Hailsham can get a three year deferral if they're properly in love. From then the book revolves around the relationships that Kathy, Ruth, and Tommy have built with each other, and how they discover what all the strange things that happened at Hailsham mean to them now.
The book is not about clones, or science fiction. It is about dealing with a limited amount of time, and the different ways of coping with the life you've been given. Tommy looks on the bright side of everything, perhaps to balance out the temper tantrums of his youth. He is always the innocent truth teller, sometimes ending up as the butt of jokes for his naivete, but nonetheless, he believes that although he never heard about the deferral rumor, it might be true.
Kathy is calm throughout her narration, accepting of the changes and problems that dot her life. Even at the end of the book, for a moment, when she allows herself a small thought of Tommy coming back to her, she keeps her feelings tightly bound. "The fantasy never got beyond that-- I didn't let it-- and though the tears rolled down my face, I wasn't sobbing or out of control." Perhaps it is her consistency and control that has extended her life far past those of her friends. This also lends itself interestingly to the voice of the novel. The book is calm, placating, even in its most emotionally charged moments. At some points it even feels numb, and although you watch as Kathy wraps her arms around a screaming, broken Tommy at the book's climax, it's as if you're sitting inside of a dirty car, and the action of the scene seems muted and far off.
Ruth goes through the most drastic changes, from selfish to self-aware. From a young age at Hailsham she seems to boss Kathy around, despite otherwise being her best friend. Once at The Cottages, she tries desperately to fit in by acting with Tommy as the other couples do, and even approaches Kathy at one point to try to nullify any chance of her trying to get together with Tommy if he and Ruth ever broke up.
But later in life, when she is nearing her last donation and runs into Kathy again, she reveals that she has procured information about how to get one of the long ago rumored deferrals, and that she wants Kathy and Tommy to go for it while they still have time, because they were the ones that were properly in love from the start, and she just got in the way.
...what I want to say, Kathy,is this. It'd be completely normal if you'd thought about, you know, what would happen if me and Tommy decided we shouldn't be together anymore. We're not about to split, don't get me wrong. But I'd think it was completely normal if you at least wondered about it. Well, Kathy, what you have to realise is that Tommy doesn't see you like that.
With Tommy and Kathy so stagnant and unchanging throughout the story, it is Ruth's transformation from a girl desperately trying to fit in and be popular to someone ashamed of her actions and in turn desperate to set them right.