This article discusses a 4-year-old girl who displayed behavioral symptoms consistent with posttraumatic stress disorder. She was recently placed in foster care due to emotional and physical neglect. During her clinic visit, she disclosed being sexually abused by her father with a knife. Results of her general and anogenital physical examinations were normal. The case discussion proposes an explanation for how a maltreated child (1) develops behavioral problems, (2) has a normal genital examination despite the history of sexual abuse, and (3) has an implausible disclosure of her father hurting her with a knife. As part of the Integrating Basic Science into Clinical Teaching Initiative series, basic science principles are the method of explanation. The case discussion is an attempt to understand the science responsible for the disease that is present and make that understanding useful for future clinical problem solving.