'That cracked mirror gave me the heebie-jeebies, and not just because it was impossible to forget what had once happened in front of it. One night, while brushing my teeth, I had the distinct impression that each half of my face was following its own separate game-plan. I'd already removed my glasses in readiness for bed, so I had to squint at the reflection to bring it vaguely into focus. One half of my face was drooling toothpaste over my chin like...