A mentally unbalanced man is obsessed with the idea that a black cat is possessed. He tortures and kills it. Later, he comes to believe that the cat has returned from the dead to kill him.

A mad stage hypnotist Dr. John Basso reverts his beautiful assistant Doreena into the physical form of a prehistoric sea monster she was in a past life. Using this power he attempts to find fame and fortune by predicting a series of murders and then using the monster to carry them out.