Claudia Diaz gets murdered in prison. Sam is picking up parts from the boatyard for his boat. OSP is investigating Diaz's death. The two women involved in the murder are killed at the hospital, and the man who shot them falls to his death when chased by Sam and Callen. Nicole DeChamps, who worked on the Diaz case with Sam, is now working at NCIS: San Diego. Sam and Callen go to talk with her. Oscar Mori was the only visitor that Diaz had. An SUV of gunmen pull up gunning for Nicole, who doesn't have a gun. After a firefight, Callen blows up propane tanks to flush out the remaining gunmen, finishing it. Alfonso Marca, Diaz's adoptive father, is trying to tie up loose ends, which includes Sam, Deeks and Kensi. Hetty takes Callen aside to tell him ATF Internal Affairs wants to talk to him. Hidoko tells Mori that the prawns he ate have parasites, to get him away from his bodyguards. Mori tells Kensi and Deeks that he gave Diaz a coded message. Callen goes to see Anna. DeChamps and Sam go to see Michael Silva, Marca's former assistant, in prison. They tell him Marca is after him for skimming money. Mosley suggests Marca may be counterfeiting yen at the ranch. Anna tells Callen that he should tell Internal Affairs the truth: that the only thing he saw was her holding her gun afterward. Silva tells them the ranch is where Marca keeps his tactical team. So Deeks and Kensi are going into danger. They roll down a cliff to escape. Sam, Callen and DeChamps arrive in support, while Kensi and Deeks hide out in a stable. They trap the shooters in a pincer movement. Mosley tells the team that a rival of Marca's was behind the murder of Diaz.