Daughters Of Darkness (1971)

Stefan (John Karlen) and Valerie (Damiele Ouimet) are taking their honeymoon a beautiful Belgian hotel near the ocean. They arrive in the off-season so have the hotel to themselves until the night Countess Elizabeth Bathory (Delphine Seyrig) shows up. The Countess brings along her secretary Ilona (Andrea Rau). Bodies start popping up all over the area and Stefan and Valerie becomes suspicious of the Countess. The Countess develops an obsession with Stefan and Valerie and what follows is the unthinkable when the four of them resort to sadism and eventually murder. Who survives the ordeal with their sanity and life?