In one of the most influential films of the silent era, Werner Krauss plays the title character, a sinister hypnotist who travels the carnival circuit displaying a somnambulist named Cesare (Conrad Veidt). In one tiny German town, a series of murders coincides with Caligari's visit. When the best friend of hero Francis (Friedrich Feher) is killed, the deed seems to be the outgrowth of a romantic rivalry over the hand of the lovely Jane (Lil Dagover). Francis suspects Caligari, but he is ignored by the police. Investigating on his own, Francis seemingly discovers that Caligari has been ordering the somnambulist to commit the murders, but the story eventually takes a more surprising direction. Caligari's Expressionist style ultimately led to the dark shadows and sharp angles of the film noir urban crime dramas of the 1940s, many of which were directed by such German émigrés as Billy Wilder and Robert Siodmak.
~ Hal Erickson, All Movie Guide