Two years before Nosferatu slinked his way across cinema screens, Robert Wiene brought us one of the first (and still best) horror movies.
The Cabinet of Dr. Caligari is about a traveling Doctor who keeps a man named Cesare locked in a cabinet. Cesare is pretty much Caligari's hypnotic slave who carries out murders and attacks at his masters command. Francis and Alan are both after a girl named Jane and when the three visit Caligari at his sideshow, Cesare predicts that Alan will be dead by dawn. When the prediction comes true, the police and Francis start investigating Caligari. Bad things happen.
The beauty of this movie is in the expressionism of the sets. The town and the carnival are twisted and amplified to nightmarish proportions, making everything seem not quite real. The other reason to stick around for this movie (besides the awesome Conrad Veidt as Cesare) is the honest to God twist ending that makes the entire story different and better.
If you have the patience to watch silent films, I would highly recommend this one as a great example of old school horror done right.