

A scientist takes the brain of dead man and revives it via electrodes as it lays suspended in a tank of liquid. Soon, the brain grows to possess enormous psychic powers and inflicts its personality upon the doctor who saved it, creating a "Jekyll and Hyde" paradigm.
Practical Effects
That pulsing brain prop deserves an Oscar nomination.
Acting
Lew Ayres goes FULL possessed televangelist.

Director
Felix E. Feist
Trivia, insights & behind the scenes
The brain prop was reportedly made of rubber and Jell-O, and reportedly melted under studio lights multiple times during filming.
This was Nancy Davis's final film before becoming Mrs. Ronald Reagan and eventually First Lady—her character watching a man destroyed by power feels accidentally prophetic.