Dr. Frankenstein and his monster both turn out to be alive, not killed as previously believed. Dr. Frankenstein wants to get out of the evil experiment business, but when a mad scientist, Dr. Pretorius, kidnaps his wife, Dr. Frankenstein agrees to help him create a new creature.
After experimenting on himself and becoming invisible, scientist Jack Griffin, now aggressive due to the drug's effects, seeks a way to reverse the experiment at any cost.
After a road accident in Hungary, the American honeymooners Joan and Peter and the enigmatic Dr. Werdegast find refuge in the house of the famed architect Hjalmar Poelzig, who shares a dark past with the doctor.
