Young adults' hopes of becoming independent are questioned when strange things begin happening in their neighborhood. As the occurrences become more frequent and aggressive they find themselves at the mercy of a murderous stalker.

In Host, Missouri, the newcomer vet, Dr Eli Rudkus, is called by a farmer to look at one of his cows. The vet finds a strange parasite in the animal and sends it to the agriculture lab to be looked into. He soon finds another one ...