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Fritz Lang's first sound film, and one of the most influential thrillers ever made. Peter Lorre — in the role that launched his international career — is Hans Beckert, a child murderer terrorizing Berlin. When the police dragnet disrupts the city's criminal underworld, the criminals organize their own parallel manhunt to catch him first. Lang's masterstroke is structural: intercutting between the two investigations, he reveals how disturbingly similar the methods of law and lawlessness really are. The film's use of sound is revolutionary — Beckert's compulsive whistling of "In the Hall of the Mountain King" becomes cinema's first great audio motif — and Lorre's final speech, a sweating, desperate plea for understanding of his compulsion, remains one of the most electrifying scenes in film history. A masterpiece of moral complexity that refuses easy answers.