Oscar nominated Lew Ayres stars as the genius brain specialist Dr. Patrick Cory. When the doctor is called to the scene of a fatal accident, he manages to extract the brain of a dying patient, keeping it alive through electrodes and his own special solution. Before long the brain - which belonged to a sinister, wealthy industrialist named Donovan - begins to exert an uncanny dominance over the once kindly scientist. Dr. Cory adopts Donovan's aggressive and paranoid personality and is compelled to carry out the brain's increasingly violent demands. When the doctor's wife (Nancy Reagan) stands in the way of Donovan's evil bidding, what will the brain make him do next?