The Bloodsucker Leads the Dance (1975)

Set in Ireland 1902. Count Marnak welcomes a modest theatre company to his isolated castle. The star of the travelling group is Evelyn, a beautiful young woman who bears a striking resemblance to the Count’s late wife. She and Marnak begin an affair, but their happiness is cut short by a series of brutal murders in which the victims are decapitated. Initially the killings a blamed on an ancient family curse, but the real culprit lurks, hopelessly insane, in the castle’s chapel. imdb