To perfect the artificial heart, the doctor must first try it on a living volunteer. "We draw out the vital heart, then chill the body," he explains to a colleague. (Chilling is, of course, one of the methods surgeons now use to stop the heart after it has been connected to the heart-lung bypass.) But the volunteer's sweetheart has no stomach for human experimentation. She tattles to the police, they disrupt the experiment, the volunteer dies, and the doctor is tried for murder.
After an eloquent defense, the doctor extends the possibilities of his research for the jury's benefit:
"The Edison or Pasteur of tomorrow need not die because of a worn-out heart. We can give him the heart of a young man who has been killed in an automobile accident!"
But the jury is unimaginative and the doctor is hanged for murder. However, he had willed his body to medical research, and it is claimed by the colleague to whom the doctor had confided the secrets of his artificial heart. After "extreme surgery to correct my broken neck," the doctor is brought back to life and spends the rest of the movie terrorizing and killing off those who had condemned him.