Corey Widen let her 8-year-old do the most normal, cheerful thing in the world—walk the dog around the block. After the girl returned home, the doorbell rang. It was the police. The cops had received a call about an unsupervised child, and had to question the mom. After doing so, they quickly dropped the matter. But then the Department of Children and Family Services picked it up again—interrogating not just Widen but her kids, other family members, and even her pediatrician. This was all due to the ridiculous assumption that one must leave no stone un-turned, even when the inciting incident...