A fleeing suspect drives into a fence guarding a Marine Corp reservation.The passenger in his care is either dead, or passed out. The driver flees on foot into the woods.
Deeks tries to save the planet all on his own and gets pricked in the buttocks by his own cactus.
The gang discovers that the passenger shows signs of having been exposed to anthrax. Hetty doesn't let Deeks go to Mexico, but rather has him go to the hospital with Kensi.
They discover that the man did indeed die from anthrax, enough to cause widespread panic.
Sam and Callen head to Mexico and encounter Agent Paolo Fuentes.
Deeks and Kensi get a lead with the help of Beale.
Sam and Callen work undercover in a fast food truck and have a cheeseburger vs veggie burger argument. A police officer stops by to check their permits, and asks for a bribe to keep them up and running. A real health inspector tires to stop the exchange, saying that not all cops are crooked.
Kensi and Deeks apprehend Alejandro, the driver of the truck. To his surprise, they reveal to him that the passenger was infected with anthrax and will most likely pass away. He's hesitant at first, claiming he can't speak English, but decides to cooperate by the end.
Sam and Callen locate a suspect in Mexico who works at a pesticide company.
Alejandro reveals more information to Kensi and Deeks, including where he met the passenger of his car. He reveals that the man was his son. Kensi and Deeks tell him he might've gotten sick because of the drugs being made in his warehouse.
All Alejandro wants is a way back to Mexico, and says he'll show them the drug tunnel in exchange.
Paolo says the public health report gave her the wrong address for the anthrax, and she gives Sam and Callen an address to a new industrial park.
Sam and Callen start to drive to the place and realize that their car has been rigged. Callen tries to avoid crashing as Sam fixes the cut breaks right in the neck of time.
Alejandro takes Kensi, Granger, and Deeks to the tunnel.
They enter and shots start firing. Alejandro is hit but requests to stay and help. He knows his son is dying and wants nothing more than to get to his grandson and daughter in law.
Granger tells Kensi and Deeks to stay where they are and not do anything stupid.
Deeks and Kensi play rock paper scissors to decide who goes first, and they discover another body.
Callen and Sam are close by to Kensi and Deeks now, so they try to meet up.
Sam, Callen, and Paolo stake out the warehouse.
The cartel start dropping bodies, from Paolo's informant to the man that worked at the pesticide company.
Kensi and Deeks rescue Tomas, Alejandro's grandson, and his mother from the cartel.
Diego Gonzalez, the "health inspector" from earlier, took the pesticide company employee's identity to cross the border.
Gonzalez recently trained as a helicopter pilot.
Sam and Callen rush the heli-pad as Gonzalez tries to make his departure with the anthrax. The win the epic showdown.
Homeland Security shows up to detain Alejandro, simply to teach NCIS a lesson for encroaching on their territory.
Deeks is stunned by the turn of events.