A woman murders her would-be rapist, setting up a delicate moral problem for her fiance, a Scotland Yard inspector. Historically if not aesthetically fascinating, this 1929 feature was Alfred Hitchcock’s first sound film. Given the technical limitations (Hitchcock’s star, Anny Ondra, couldn’t speak English, and had to lip-synch with a British actress standing off frame), the aggressive experimentation with the sound track is remarkably effective. Like most of his British films, Blackmail is a sign of things to come rather than Hitchcock at his height, but it shouldn’t be missed.