The murder of an adolescent girl from Mexico, found dead in the Los Angeles River, proves difficult and painful for Brenda and her team. At first, a known sex-offender seems the likely candidate, but questions arise about why the girl and her mother were brought to the US, leading the investigation in another direction. Soon, the girls backpack suggests the girls uncle or the family for whom the mother worked may have been involved, A search of the house suggests one of the family is the murderer, but which one? An end-run by the family, determined to protect the killer, takes Brenda to Mexico, where she must use all her resources, Fritz and Mexican law to finally bring the killer to justice. The usually cantankerous Dr. Crippen shows his softer side as he briefs Brenda following the autopsy, in a scene representative of the way in which the violent death of a child impacts the police.