NCIS: Los Angeles is a drama about the high-stakes world of a division of NCIS that is charged with apprehending dangerous and elusive criminals that pose a threat to the nation's security. By assuming false identities and utilizing the most advanced technology, this team of highly-trained agents goes deep undercover, putting their lives on the line in the field to bring down their targets.
After Hetty turns in retirement papers and then disappears, Executive Assistant Director Shay Mosley arrives in Los Angeles to oversee the team and immediately makes staffing changes. Also, still mourning the death of his wife and living in a trailer on the beach, Sam is adamant that Callen find a new partner.
Sam goes undercover as a day trader after a prominent investment banker with ties to a Russian oligarch is murdered. Also, one of Callen's aliases is the victim of credit card theft, and Mosley is concerned it signals something bigger.
The NCIS team must locate a group of unknown assailants who illegally crossed the border and attacked California Highway Patrol officers. Also, Homeland Security sends over Specialist Sydney Jones, Nell's older and bossy sister, to assist NCIS with the case.
The team investigates a ransomware attack that takes out the entire power grid for west L.A. and paralyzes the city. Also, as the first holiday season since the death of Sam's wife approaches, he struggles to find the best way for his family to celebrate.
Callen, Sam, Kensi and Deeks join Hetty's team from the Vietnam War, Sterling Bridges, A.J. Chegwidden and Charles Langston, in a dangerous and off-the-books rescue mission to save Hetty from her captors in Vietnam. Also, Mosley calls in Nell's sister, homeland security specialist Sydney Jones, to assist the team in Los Angeles with processing evidence connected to Hetty's time in Vietnam.
While investigating a missing person's case, the team uncovers a killer who puts on shows for high-paying voyeurs. Also, Mosley assigns Callen as her partner on a joint ATF mission to apprehend someone from her past.
Callen and Sam join forces with Anna Kolcheck and the Bureau of Alcohol, Tobacco and Firearms (ATF) when Arkady Kolcheck warns NCIS that a notorious international weapons dealer has returned to the states. Also, the case requires Eric to go undercover as a bank IT technician.