On Friday, June 13th mild-mannered English professor George Kingsley (Stanley Ridges) is rundown by gangster Red Cannon, himself shot during a gun battle with former associates. Kingsley’s brain is severely damaged, so his friend and fellow professor, Dr. Ernst Sovak (Boris Karloff), transplants part of the wounded gangster’s brain to save Kingsley’s life (and prove his theories in the bargain). Sovak’s motives aren’t entirely pure, however, as Red hid most of his ill-gotten-gains and Sovak hopes that he will be able to get the information out of Kingsley when he recovers. To aid in the process, Sovak takes Kingsley to New York, deliberately bringing him to Red’s old hang-outs in the hopes of awakening Red’s consciousness. Sovak’s theories prove correct and soon Kingsley and Red are doing the Jekyll and Hyde thing, with the main trigger for Red to take over being the sound of sirens. Red uses his new body to gain terrible revenge on his former associates, strangling them one by one, and to see his girl, nightclub singer Sunny Rogers (Anne Nagel). Rogers, disturbed by Kingsley’s intimate knowledge of Red’s affairs, agrees to bait a trap for Red/Kingsley with Eric Marnay (Bela Lugosi), Cannon’s former partner. Marnay does not believe Red is back, but that Red gave Kingsley the location of his loot in return for enacting Red’s revenge. Will Red remain dominant long enough to find the money and defeat Marnay and his thugs? Will Sovak be able to return Kingsley to control and keep him out of jail?![]()
