She wanted to say, no. She wanted to say, I have a son, there is a child, this cannot happen. Because you know that no one will ever love them like you do. You know that no one will look after them like you do. You know that it's an impossibility, it's unthinkable that you could be taken away, that you will have to leave them behind.

In the course of writing a book I'll produce loads of pieces of paper to help the novel itself. Diagrams, charts, family trees. And at the end of each book I'll pack it all away. It takes me a while to do it - it's like a relationship that way; there's a period of letting - go, of grief, in a way - but then I box it up, label it, and put it in the attic.

I have two sisters, and I think siblings are always going to be irresistible for novelists. They have been throughout time and they'll continue to be.

We all have a family, whether we like it or not; we all come from somewhere, and there's something strange in the way you have, with siblings, two or three personalities yoked together for life. You grow up thinking those family relationships are set in stone and then you get older and realize they're not. They're always shifting.

Why isn't life better designed so it warns you when terrible things are about to happen?

The role you've been ascribed in childhood can twist or break apart or seem outgrown, especially when you have your own family and begin to see your own childhood from a different angle. You remember. You reassess. I think that was the kernel of the novel for me. This idea that you change but that your family, the people you were born into, might find that change hard to accept. You no longer fit the mold you've always been ascribed. When the adult children in the book converge back on their small family home there's a sense that they don't fit there anymore.

I met a retired police detective. And he said to me that the interesting thing about heatwaves, from a police perspective, is that the number of people who just walk out of their lives when the weather gets unbearable is astronomic. He said the police prepare themselves for it - for a huge rise in the instances of missing persons. People choose to disappear when it's hot. It was fascinating.