M (German: M – Eine Stadt sucht einen Mörder— M – A City Searches for a Murderer) is a 1931 German thriller film directed by Fritz Lang and starring Peter Lorre. The film was written by Lang and his wife Thea von Harbou 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 timeless classic, the film was deemed by Lang to be his magnum opus