After spending several years exploring more contemporary genres, director Mario Bava (Black Sunday) returned with Baron blood to the gothic as a setting for a gruesome thriller. Working with producer Alfredo Leone, Bava crafted a film that is loyal to the bylaws of traditional horror, but is infused with a more modern visual style. An American professor (Antonio Cantafora) travels to the estate of his ancestor, the sadistic Baron Otto von Kleist, seeking the truth beneath his notorious reputation. When he and his assistant Eva (Elke Sommer) read aloud an ancient incantation, the Baron's spirit is resurrected, leading to a series of violent deaths within the haunted castle.