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.
A group of children are playing an elimination game in the courtyard of an apartment building in Berlin[5] using a chant about a child murderer. A woman sets the table for dinner, waiting for her daughter to come home from school. A wanted poster warns of a serial killer preying on children, as anxious parents wait outside a school.
Little Elsie Beckmann leaves school, bouncing a ball on her way home. She is approached by Hans Beckert, who is whistling "In the Hall of the Mountain King" by Edvard Grieg. He offers to buy her a balloon from a blind street-vendor. He walks and talks with her. Elsie's place at the dinner table remains empty, her ball is shown rolling away across a patch of grass, and her balloon is lost in the telephone lines overhead.
In the wake of Elsie's death, Beckert sends an angry letter about his crimes to the newspapers, from which the police extract clues using the new techniques of fingerprinting and handwriting analysis. Under mounting pressure from city leaders, the police work around the clock. Inspector Karl Lohmann instructs his men to intensify their search and to check the records of recently released psychiatric patients to look for those with a history of violence against children. They stage frequent raids to question known criminals, disrupting underworld business so badly that Der Schränker ("The Safecracker") calls a meeting of the city's criminal bosses. They decide to organize their own manhunt, using beggars to watch and guard the children.
The police discover two clues corresponding to the killer's letter in Beckert's rented rooms. They wait there to arrest him.
Clasificación [ CM DVD 00525] Disponible en DVD, 4 Piso BJB)