If you haven’t finished The Last House on Needless Street yet, please don’t read on—what follows is one long spoiler.

This is how I came to write a book about survival, disguised as a book about horror. In the summer of 2018 I was writing about a cat and I couldn’t work out why. I had always been fascinated by the apparent ease with which those who lack empathy form strong, passionate attachments with their pets. Serial killer Dennis Nilsen’s dog, Bleep, was the only creature he could be said to have had any functional relationship with. He loved Bleep and the fate of the dog was the only thing he was concerned with after his arrest. So I thought, Maybe this is the right story, the one I should be working on. Olivia the cat, who lives with Ted and gives him comfort, even though he took a young girl named Lauren and keeps her captive. But it wasn’t working. Ted didn’t seem like a murderer, or a kidnapper. I kept finding pockets of compassion for him. His story felt like one of suffering and survival, not like that of a perpetrator. And Olivia didn’t really behave like a cat. She did have catlike qualities but her voice seemed neither human nor feline, but something other. She seemed like a part of him. So did Lauren, the girl who was ostensibly Ted’s prisoner.

I was researching the effects of childhood abuse when I came across a video online of a young woman named Encina, who has dissociative identity disorder, discussing her condition. She talked with great frankness and compassion about her younger alter. She treats her as her child, adopting a maternal attitude, taking care of her, making sure she’s not scared, or faced with activities she can’t accomplish, like driving. The younger alter came forward, for a time, and spoke. She talked about how lonely she is, because no other children want to play with her, because the body she’s in is big and they don’t understand. I felt that my outlook on life changed as I watched them talk. The video is listed in the bibliography (What It’s Like To Live With Dissociative Identity Disorder (DID)). I realized that the book I was writing had never been about a cat named Olivia, a girl called Lauren and a man named Ted. It was about someone who had all these personalities within them. It wasn’t about horror but about survival and hope, and how the mind copes with fear and suffering.