On Halloween night, Laura and Mary get permission from their parents to walk into town and pull a little prank at the Mercantile. Laura's imagination runs wild when she peeks into the Olesons' window and witnesses Nels committing an unspeakable crime. Scarred by what she has seen, Laura can't get anyone to believe her.

Although he is still struggling with his wife's death, Lansford adjusts well in Walnut Grove and bonds with everyone in the family, especially Laura. Unfortunately, another tragedy threatens to tear them all apart just as things are really starting to look up.