When Dr. Robbins' friend Gabriel Ortiz, a wealthy Las Vegas businessman, calls upon his help to determine how his teenage daughter Ana died, Robbins and Nick head to the border city of Arquero, Mexico where her body was found. Dr. Blanco, the coroner at the Arquero morgue, believes Ana overdosed on cocaine, but traces of corn husk found on her body connect her to the scene of a cartel hit that took place on a corn farm. Despite warnings of cartel-on-cartel crime in that area, they venture there to investigate and ascertain she was dumped there by a semi-truck hours after the shooting. The CSIs rule out a drug overdose when heavy metal poisoning is found to be the cause of death.Meanwhile, Sara and Greg are alerted to two concrete-caked human bodies buried in a garage. They are startled to learn the female victim, Claire, had the same thallium poisoning as Ana. They put the pieces together to determine that both women were romantically involved with a portrait artist named Keith Garner who was their high school art teacher at different times. Keith poisoned Ana after she pulled away from him and left her body in the truck to be transported to Arquero. Upon learning of Keith's connection to Ana, Claire was unknowingly poisoned and tried to run, but both she and her brother-in-law were shot and hastily buried. The team intervenes as Gabriel is attempting to kill Keith and they also make a chilling discovery of five other victims' portraits.