Night of the Devils

The film begins with an unknown man stumbling into hospital. He doesn't make any attempt to identify himself, but soon after an unknown woman turns up and he begins to panic. From there we go back in time as the man remembers the events that lead up to him stumbling into the hospital. It emerges that he had a break down and was forced to stay with a family out in the woods. They are clearly hiding something right from the start and we soon find out that there's something preying in the woods. An earlier cinemadaptation of The Wurdalak, starring Boris Karloff, was incorporated into the omnibus Black Sabbath (1963).