Which is the Virgin? Which is the Vampire?

While dabbling in Satanism, Count Karstein resurrects Mircalla Karnstein who initiates him into vampirism. As a rash of deaths afflicts the village, Gustav the head of Puritan group leads his men to seek out and destroy the pestilence. One of his twin nieces has become inflicted with the witchcraft but Gustav's zeal and venom has trapped the innocent Maria, threatening her with a tortuous execution, whilst Frieda remains free to continue her orgy of evil.