A snake-like parasite crawls into the uterus of an abused woman and circus performer named Yanka. The parasite demands human blood from Yanka who is first reluctant, but then finds that the only relationship she has is with the parasite. Yanka commits murders to devour the victims blood in order to nurture the parasite. The parasite tells her that it is a creature that will replace man as the dominant species on the planet in five million years, and must be released in the ocean. The creature is eventually released in the sea where it abandons Yanka.