When the corpse of Mexican cartel boss Miguel Barbosa is stolen from a Tijuana morgue under suspicious circumstances, the NCIS:LA team is brought on to locate a potential mole in the Navy & DEA backed task force that took Barbosa down in the first place. Sam and Callen speak with Special Agent John Ness, who was hunting Barbosa for the last decade, to get information about the case, but they hit a snag when Ness is poisoned in his own office and dies. Meanwhile, Kensi and Deeks head down to Tijuana to locate a cartel informant named Javier Ramos, who was very close to Barbosa. They save him from rival cartel fire and interrogate him, and they are convinced that Barbosa is actually still alive after hearing Javier's story. When given the choice between entering witness protection for the rest of his life or helping in an NCIS sting to take down Barbosa once and for all, Javier opts for the latter and gets captured. He's taken to Barbosa, who is still very much alive, and the NCIS:LA team tracks him down and neutralizes Barbosa and his men.