Clive travels to the ancient Church of St. Mary's Troston, where the walls are scored with medieval demonic symbols. Mary-Ann tries her hand at spells and curses, learning why demons really weren't very smart. Clive tries to understand why people 600 years ago truly believed that demons walked the earth doing the devil's work. The two discover that these evil creatures transformed into something very real and very human - witches. What drove such intense levels of superstition in our ancestors? And were people really practicing black magic?