The OPS is called in when two U.S Marines are kidnapped and one murdered along the U.S-Mexico border.
The team initially believes drug cartels are involved so Sam risks using a no longer viable cover to meet a former contact, Memo Torres, who may have info on the missing Marines.
Sam knows the Marines don't have much time but Memo isn't cooperating. Callen photographs a limo leaving Memo's shop which leads them to a businessman, Donald Wexler.
Wexler tells them he has been paying off Memo for protection against the drug cartels, calling it the price you pay for doing business across the border.
Meanwhile, Kensi and Deeks are in the desert following the SUV tracks that lead away from the scene ... and to a desert compound.
Kensi spots the two missing Marines being hustled into a waiting plane and knows that if they get on that plane they will never see them again.
She calls in their coordinates then Kensi and Deeks move in to rescue the Marines. Deeks creates a diversion and Kensi pulls the Marines to cover. Just as they are about to be ambushed by grenades, Callen, Sam and the Marines arrive.
The kidnappers were not drug cartel members but mercenaries hired by Wexler. He thought if he could frame the cartels for the attack on the U.S Marines, the U.S military would then get involved in taking out the cartel.
In turn, this would mean better business for Wexler.
Kensi and Deeks spend a lot of time togetherand open up about their relationships with their fathers. Nate heads back where he was before, presumably to Afghanistan or Iraq.