Following an atomic war, the human survivors live underground, building machines to do their work for them. Years later, they return to the surface, leaving the machines behind, but the machines begin to think for themselves, and rise up to conquer the surface world.
A woman with a terminal illness falls in love with a man named Walter who is indifferent to her. She offers him everything but he says he would never marry a witch. She denies being a witch and asks for a way to prove it. He tells her to go to Black Mountain where witches and demons hold a Black Sabbath. If they reject you, you're not a witch. She goes, and finds to her surprise, herself dancing with demons. A figure appears and proclaims he is her master and she was not a witch when she came to Black Mountain, but she is one now and will live forever with her malady. The figure is revealed to be Walter.