Blackmail (1929) is a British movie which was made on the cusp of the sound era. Hitchcock, who was the only British silent film director who didn't stink, decided to make it into a talkie midway through filming. His lead actess had a foreign accent, so he dubbed her voice by having a British actress speak the lines while Anny Ondre moved her lips. She plays a blond murderer who is a victim of blackmail by a voyeur. There's a scene in the dining room in which the woman, her boyfriend, and the blackmailer are all together, and the tension is just dreadful. The sound technology is primitive, but when you need it, the dialogue is there. If you like Hitchcock's later stuff, I recommend this one. You'll be amazed how consistent his quality was.