Alfred Hitchcock's 3-D film, although the 3-D version seems really rare now; unfortunately, the new DVD is just plain-old 2-D.
Anyway, it's a cool, engaging story of blackmail, attempted murder, plain-old-regular murder and frame-ups. And one of the most interesting things about it is that even though the protagonist is clearly the Bad Guy, you still find yourself pulling for him, wondering whether or not he'll be found out. A really cool film. It was based on a play, although Hitchcock made it his own. I love this one.