Thriller directed by Fritz Lang stars Peter Lorre in his breakthrough role as serial child killer.
The film's screenplay was written by Lang and his wife Thea von Harbou and was the director'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. It is widely considered one of the greatest films of all time, and an indispensable influence on modern crime and thriller fiction.