At night, a carnivorous, shape-shifting alien named Kator lands in the woods of rural England. The vanguard of an invasion force, his mission is to evaluate the suitability of humans as a source of food for his species. Stumbling across Anderson and Sandy, a couple having a tryst in their parked car, he kills both and assumes the appearance of Anderson. The next morning, he encounters Jessica-Ann and Josephine, a lesbian couple who live in a nearby manor house. Although Jessica owns the property, having inherited it from her Canadian parents, the dominant of the pair is Jo, who is unusually possessive of Jessica and deeply suspicious of men. Simon, Jessica's boyfriend, has mysteriously disappeared. The women are vegetarians and live in seclusion with only a few chickens and a pet parrot, Wally, for company.