The son of Dr. Frankenstein (Basil Rathbone) returns to his ancestral castle 25 years after his father's death. There he meets shady blacksmith Ygor (Bela Lugosi), who urges the young doctor to take up where his father left off. He revives the monster (Boris Karloff), but when several villagers turn up dead (villagers who just happen to have served on the jury that sentence Ygor to the gallows), chaos ensues as the villagers revolt against Frankenstein and his creation.