M (German: M – Eine Stadt sucht einen Mörder— M – A City Searches for a Murderer) is a 1931 German drama-thriller film directed by Fritz Lang and starring Peter Lorre. Lang and his wife Thea von Harbou wrote the film and was the director’s first sound film.
The film revolves around the actions of a serial killer of children and the manhunt for him, conducted by both the police and the criminal underworld. Now considered a classic, Fritz Lang deemed the film to be his magnum opus. (Wikipedia)
