M is a 1931 German drama-thriller directed by Fritz Lang and starring Peter Lorre. It was written by Lang and his wife Thea von Harbou and was Lang's first film with sound, although he had directed more than a dozen films previously. The film has become a classic which Lang himself considered his finest work. The film is set in Berlin in 1931. The police are looking for a child murderer and start rounding up all the criminals they know. The city's gangs decide to try and catch the killer themselves. They do just that and try him in their own court. The police rescue him and arrest him so that he can stand trial again. The film ends with a warning to parents to watch over their children.
M is supposedly based on the real-life case of serial killer Peter Kürten, the "Vampire of Düsseldorf", whose crimes took place in the 1920s. Lang denied that he was influenced in any way by this case. Lang told film historian Gero Gandert in a 1963 interview: "At the time I decided to use the subject matter of M there were many serial killers terrorizing Germany." M premiered on May 11, 1931 in a version lasting 117 minutes. The original negative is preserved at the Federal Film Archive in a 96-minute version. In 1960 a shortened version was released lasting 98 minutes. The original 1931 version was ranked #33 in Empire magazine's "The 100 Best Films Of World Cinema" in 2010.