Soldiers in a rural English town are being brutally murdered by an unknown creature. Two nearby sisters realise they might understand what's happening.

French au pair Monique goes to work for couple Jean and Bill. She takes time to care for the children before getting to know husband and wife intimately. Bill soon notices Jean's libido has spiked. After Bill sleeps with Monique, he comes home one day to discover the women in bed together.

A shy, lonely American girl marries a charming man she meets while on vacation in England, unaware that he has sinister plans for her.