Have you ever thought of murdering somebody? I suppose most of us have, but there's something that's different between thinking about it, and carrying it out. Something that's different, but not that you can see or recognize, or that may give you a warning. For example, a murderer may have stood next to you in the lift this morning, or the man who asked you for a light for his cigarette, or sat next to you in the cinema, or shared the same table at a restaurant. There was nothing to show he was a murderer...