This is my favorite Hitchcock film. It's beautifully filmed and Robert Walker is genius as the psychotic Bruno Anthony. He's so convincing as the affable fellow on the outside that when you discover his crazy nutball center, you feel as duped as Guy Haines. I just love the idea of this story - an instance of casual, everyday small talk going so horribly wrong.
Also, Patricia Hitchcock's performance is a treat. She's so dorkily adorable. This is one of those films that I have to watch at least once a year.