A mad scientist uses an artificial heart pump he invented to seek revenge after he is executed.

Obsessed with bringing the dead back to life, Dr. Henryk Savaard perfects a mechanical device that suspends and restores life at will. The doctor is working on his first patient, a medical student who has volunteered for the experiment, when the police, alerted by the student's sweetheart, break into the lab and refuse to allow the doctor to bring his human guinea pig back to life. Convicted and sentenced to hang for murder, the doctor vows revenge on the judge, jury and district attorney. After the hanging, the doctor's trusted assistant claims his lifeless body and, using the mechanical device perfected by Savaard, brings him back to life. Foresaking science for revenge, Savaard lures his persecutors one by one to his house and murders them. After the death of the sixth juror, reporter "Scoop" Foley deduces that the killings are related to the doctor's trial, and he goes to the Savaard house, where he finds the surviving members of the trial imprisoned by the vengeance-crazed doctor. Savaard is working on his ninth victim when his daughter Janet interrupts his plans. In the confusion, Janet is electrocuted and Savaard mortally wounded. Summoning the strength to apply his lifesaving technique to his own daughter, Savaard then destroys the apparatus and dies of his injuries, taking the secret of perpetual life to his grave.