The legendary Loreley has been living for centuries in a grotto beneath the river Rhein in Germany. Every night when the moon is full, she turns into a reptile-like creature craving for human blood. When one girl after another of a nearby boarding school is killed by her, a hunter named Sirgurd is engaged to kill the monster.

An evil ruler uses witchcraft and evil spirits to keep his subjects in line, but the his reign of terror prompts the people to revolt.