Originally aired November 1, 1976. On Halloween night, Laura and Mary get permission from their parents to walk into town and pull off a little prank at the mercantile. Laura's imagination runs wild when she peeks into the Olesons' window and thinks she sees Nels killing Mrs. Oleson. Scared by what she has seen, Laura can't seem to get anyone to believe her. Her friend, Carl, the only person to believe her, joins the search for evidence to solve the crime. Meanwhile, Mrs. Oleson has gone away, so the two really think that she has been murdered. When Nellie and Willie hear the story, they don't believe it but decide to scare Laura and Carl by saying that their father has been digging in the cellar.