The central character is a teenage boy who lives with his parents. At one point he goes downstairs, sees his parents are watching a film where a man is following someone along a foggy street, and you see the man's feet and the railings he is walking past. The boy then sneaks out of his house.
What is the book? Reason being I think I've just seen the film and it made me think of that scene in the book. I don't know why.