The female cop who trained Benson is brutally assaulted during a routine patrol call. When SVU investigates, the woman is less than cooperative. Internal affairs gets involved and it quickly becomes apparent that there is nothing simple about the case. Eventually, the unit learns that Benson's mentor was a mole in an IA investigation and was assaulted by her fellow cops once they found out her secret. SVU must then wade through the ensuing police cover-up to bring the cops to justice.