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 classic, Lang regarded the film as 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.