M (German: M - Eine Stadt sucht einen Mörder — "M - A city looks for a murderer") is a 1931 German drama-thriller film directed by Fritz Lang and starring Peter Lorre. It was written by Lang and his wife Thea von Harbou and was the director's first sound film.

Now considered a classic, the film was deemed by Fritz Lang as the finest work he'd ever done.

The movie revolves around Lorre as a serial killer preying on children and the psychological repercussions of the murders.This story of a serial killer in Weimar-era Berlin, Germany embodies the social criticism and terror of the time immediately before Nazi rule.

Lang's unique use of lighting and shadows to create suspense foreshadows Film Noir.

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