I wanted to write a very simple story about a boy, a wolf, a girl, a bear and a forest, so I thought I might set it in the past. I didn't realise that it went back to when I was 10: I used to love the Stone Age when I was a kid and wanted to live in it, and I got rid of my bed and slept on the floor, but I didn't remember it.

The most remote place I've been to was in Greenland. I remember setting out for a solo hike from a small cabin, itself several hours' boat ride from the nearest settlement.

I've wanted to write a ghost story for years, and my main aim was to write the most frightening ghost story that I could think of.

I sometimes wonder why I do so much research - I look at other successful writers, and I think it must just be so relaxing to write about flying horses or something, but I have to make it plausible.

What a fine line there is between artistry and insanity. There's no formula for it, and I think a lot of people when they're around you - even those closest to you - when you're in that whirl of creativity and you're grabbing those things out of the air, there's no rational process.

I lived in the States from 1996 till 2000. I attended the Berklee College of Music in Boston in 1997. But I wasn't the most hard-working student. I rarely went to school. At that time, I seriously doubted that you could learn creativity in school. Music isn't something you can just learn from other people. Sometimes I regret missing classes.

I don't know if I can see myself writing another 'Saw' film. It's such a special part of my life, and I almost don't want to ruin it by going back.

I go to the theater and dream. You learn your lines, and that gives you the security to allow the imagination and heart to come out.