Mysterious and unearthly deaths start to occur while Professor Saxton is transporting the frozen remains of a primitive humanoid creature he found in Manchuria back to Europe.

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.