A journalist, sent to write a series of articles on ancient estates, uncovers the existence of a vampire - and a coven of Satanists.
The vampire was the last Lord of Barnstable Manor, which has become the headquarters for the Satanists. His daughter is a school teacher in the village but is unaware of her father's real identity.
Unknown to him, the vampire also has another daughter who is a prisoner of the Satanists and is being reared to become the Virgin Bride of Satan.
Due to sapphic complications between the sisters, the Satanists kidnap them both and force them to swap places in the wedding ceremonies.
The vampire joins forces with his hunters to rescue the girls from the Devil's followers, the conflict climaxing during the Black Mass to celebrate the return of Satan.