Paul Raden (Albert Dekker), hopelessly insane son of Maxim Raden, hated owner of the Radentown mills, is in a strait jacket in a secret room in the family mansion, while the body of his father is lowered into a grave. Twenty-five years earlier, the brutal father had hurled Paul against a wall when the young boy had tried to defend his mother and, with his brain injured forever, Paul's last memory, before descending into the shadows on insanity, was his mother's agonized scream. At the graveside are Dr. Ben Saunders (Harry Carey), Paul's twin brother John (Albert Dekker) and John's wife Elaine (Frances Farmer). Pompey (Ernest Whitman'), the family servant who has cared for and guarded Paul and kept the family secret for a quarter of a century,watches from afar. That night Dr. Saunders tells John that his twin, who he thought dead, is alive as the father, refusing to commit him to an institution, had bribed the doctor to sign a false death certificate and then bury another child's body as Paul. John and the doctor visit Radenhouse and find Pompey strangled and Paul vanished. While they search frantically for Paul, the latter revels in his freedom and falls in love with the first girl he meets, Millie Pickens Susan Hayward), an unemployed mill worker. He wanders into a honky-tonk filled with dancing jitterbugs, where a pretty blonde, Peggy Nolan (Jean Phillips), flirts with him. Her body is found the next morning near the closed-down Raden Mills. Terrorized by the second murder and the thought that a homicidal maniac is on the loose, the town goes mad with fear and greed when Dr. Saunders tricks John into offering a $5,000 reward for the killer. Millie swipes her late father's revolver and persuades Paul, whose demented mind has forgotten the murders, to accompany her to Radenhouse on her hunch that the murderer is hiding there.