CBS

Season 13: Episode 19 - Backfire

Backfire: The CSIs are called in to investigate a triple homicide and are shocked to find a 6 year-old girl, Molly, when they arrive at the crime scene. Molly is traumatized because her uncle, Steve, is among the three victims, who appear to have been killed after being savagely beaten, and Molly's mother, Grace, is missing. Preliminary evidence suggests the two other male victims were a tandem of robbers who had been involved in a string of local burglaries, so the CSIs begin to suspect that this was a revenge killing of some sort. After following a string of leads, including a mini-case involving a man who managed to accidentally set himself on fire and lock himself in his trunk, the CSIs finally uncover a crucial piece of evidence: a book in Molly's possession with a damning recording inside. The recording features Grace arguing with her father, Gary, about his shady past, hinting that he molested Grace and Steven when they were younger. Eventually, the CSIs discover that Gary's mother, Agnes, conspired with her lowlife boyfriend, Tony Rush, to recover that recording and kill her grandchildren. Agnes and Tony are arrested, and Russell personally ensures that Molly is sent to live with caring family members.