Donovan's Brain (1953) on Netflix

Plot summary

Dr. Patrick Cory keeps a monkey's brain alive in a laboratory at the mountain retreat he shares with his wife Janice. When a plane crashes near the cabin, rescuers bring the only survivor, the injured businessman Warren H. Donovan, to Cory for help. His heart stops, and Cory takes the brain into his research, suspending it in a tank of electrified saline solution. Cory and his assistant, Dr. Frank Schratt, look into Donovan's past and find that the millionaire was a ruthless man. One night a message in Donovan's handwriting appears on a page Cory wrote, and Cory becomes certain that Donovan's mind survives in the tank. He sets out to communicate with it.