A missionary schoolteacher haunted by experiences with witchdoctors in Africa (played by Joan Fontaine) finds employment in an isolated English village and begins to believe witchcraft is occurring there. Kay Walsh portrays the town’s well-educated leading woman. “The Witches” (1966), also called “The Devil’s Own,” is a little-known Hammer Horror film that clearly had an impact on the later, beloved movie “The Wic…