M (1931 film)''M'' is a 1931 German mystery suspense thriller film directed by Fritz Lang and starring Peter Lorre (in his third screen role) as Hans Beckert, a serial killer who targets children. An early example of a procedural drama, the film centers on the manhunt for Lorre's character, conducted by both the police and the criminal underworld.
The film's screenplay was written by Lang and his wife Thea von Harbou, and it was Lang's first sound film. It features many cinematic innovations, including the use of long, fluid tracking shots, and a musical ''leitmotif'' in the form of "In the Hall of the Mountain King" whistled by Lorre's character. Now considered a timeless classic, the film was deemed by Lang to be his magnum opus. It is widely considered one of the greatest films of all time, and an indispensable influence on modern crime and thriller fiction. Provided by Wikipedia