Tampering with life and death, Henry Frankenstein pieces together salvaged body parts to bring a human monster to life; the mad scientist's dreams are shattered by his creation's violent rage as the monster awakens to a world in which he is unwelcome.

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.

One of the sons of late Dr. Henry Frankenstein finds his father's ghoulish creation in a coma and revives him, only to find out the monster is controlled by Ygor who is bent on revenge.

Frankenstein's unscrupulous colleague, Dr. Bohmer, plans to transplant Ygor's brain so he can rule the world using the monster's body, but the plan goes sour when he turns malevolent and goes on a rampage.

Deranged scientist, Gustav Niemann, escapes from prison and overtakes the director of a traveling chamber of horrors, soon reviving the infamous Count Dracula, the frozen Frankenstein Monster, and the Wolf Man.