M was directed by Fritz Lang in 1931. It is film is nothing less than a masterpiece, a highly structured and stylized film about a serial killer. It created the serial kill genre, which includes such entries as Psycho and Silence of the Lambs. Alfred Hitchcock (the director of Psycho) was a disciple of Lang as were Jacques Tourneur (The Leopard Man (1943)) and Michael Powell (Peeping Tom (1960.))
A group of children are playing a game involving a song about a child murderer. This foreshadows the appearance of Hans Beckert (Peter Lorre), a serial killer — and, it is implied, a paedophile — who preys on children in 1930s Berlin. Initially the audience does not see his face; they merely see his shadow, shots of his body and hear him whistling "In the Hall of the Mountain King" by Grieg as he buys a balloon from a blind man and gives it to a little girl named Elsie Beckmann (Inge Landgut). In the next scene, her mother (Ellen Widmann) searches frantically as the audience sees the balloon ensnared in telephone lines, and subsequently floating away.
Meanwhile, the police, under Inspector Karl Lohmann (Otto Wernicke), pursue the killer using then state of the art techniques such as fingerprinting and handwriting analysis. They also stage raids and question known criminals. This affects underworld business and some of the top crooks decide to get rid of the killer themselves so they can resume "business". The criminals enlist the help of the citys beggars to keep watch over the children and find the killer. Thus a race develops between the police and the criminals to catch the killer, who is completely unaware of what is happening. He makes the mistake of whistling his tune again near the same blind balloon salesman. The blind man tells one of the criminals, who tails the killer using a beggar network. Desperate for a way to track him, one of them marks a large letter M (for "Mörder", meaning murderer in German) onto his own hand with chalk. He then claps Beckert on the shoulder, transferring the letter M onto the killers coat...
Peter Lorre as Hans Beckert. M was Lorres first major starring role, and it boosted his career, even though he was typecast as a villain for years after in films such as Mad Love and the film adaptation of Crime and Punishment. Before M, Lorre was mostly a comedic actor. After fleeing from the Nazis, he landed a major role in Alfred Hitchcocks first version of The Man Who Knew Too Much (1934), picking up English along the way.
Otto Wernicke as Inspector Karl Lohmann. Wernicke made his breakthrough with M after playing many small roles in silent films for over a decade. After his part in M, he was in great demand due to the success of the film, including returning to the role of Karl Lohmann in The Testament of Doctor Mabuse, and he played supporting roles for the rest of his career. Gustaf Gründgens as Der Schränker. Gründgens received acclaim for his role in the film and established a successful career for himself under Nazi rule, ultimately becoming director of the "Staatliches Schauspielhaus."