Warlock Moon (1973)

Young lovers John and Jenny decide to go for a drive in the countryside one day when they happen upon the remains of a long-abandoned resort spa. After doing some exploring, they find that an elderly woman, Agnes Abercrombie, is living in the crumbling building. As they learn the gruesome history of the place, involving cannibalism and a ghost bride, Jenny becomes the victim of violent attacks and supernatural visions. But no one will believe her and now she's stuck in the dilapidated resort overnight. Will she survive until morning?