A drone strike on a bomb-making compound in Afghanistan reveals the body of a recently retired Marine, leaving the NCIS: LA team to investigate why the Marine returned to Afghanistan and whether or not he betrayed the country he fought for.
The NCIS: LA team investigate a compromised intel operation after four people connected to the classified project are killed at a diner explosion. As Deeks and Kensi are on the trail of those involved, they learn that a wayward teenage girl might be related and Kensi can’t help but be empathetic to her situation.
The NCIS: LA team investigates the tragic death of a U.S. senatorial candidate’s staffer who is run over crossing the street. The high-profile case becomes a matter of national security as the agents must determine whether it is an isolated tragic incident or a politically connected plot that might put others in danger.
When a CIA agent who worked with Sam Hanna over eight years ago seeks his help and is soon found dead of an apparent suicide, Hanna and Callen suspect foul play and a bigger conspiracy. Meanwhile, Deeks finds his inner “dog whisperer” with Kensi as the two go undercover and enter a dog show with a prized poodle.
The NCIS: LA team heads to the beach to question the possible link between a surfer, an Internet video and a dead Naval tech scientist. Meanwhile, as Callen and Hanna investigate the victim’s intelligence connections, Deeks and Kensi go undercover to catch their suspects and some waves.
The NCIS: Los Angeles team investigates the strange and brazen heist executed by gunmen in costumes that could directly impact the U.S. economy. Meanwhile, as Deeks testifies on a case, Granger insists on partnering up with a very reluctant Kensi.
Callen, Sam, Kensi and Deeks spend Christmas aboard an aircraft carrier investigating the death of a fellow NCIS special agent. Meanwhile, Nell and Eric make the most of the holidays back at headquarters and Hetty takes a trip.
A former defendant of Deeks is targeted for discovering information that could dismantle a lucrative car shipping operation with links to a global terrorist ring. Meanwhile, the NCIS: LA team tackles the large-scale stolen car operation from the inside when Kensi goes undercover in an auto body shop.
A distraught widow is suspicious of the circumstances surrounding her Marine husband’s last battle and Sam and Callen help to determine if there has been a cover-up. Meanwhile, Hetty summons Operational Psychologist Nate Getz to be her “pawn” and the rest of the NCIS: LA sense another evaluation on the horizon.
Callen and Sam fly to Idaho and join forces with NCIS: Red, a mobile team of agents who live together and investigate crimes in various locations, when a murder weapon found there matches one used in a national security case in Los Angeles.
While the LA team chases leads digitally and locally, the NCIS: Red team travels in their mobile trucks, nicknamed "Laverne and Shirley", in a race to track down a cunning terrorist before he disappears.
When cyanide in a communal water jug lethally poisons a lieutenant and leaves a Navy pilot in serious condition, the NCIS: LA team investigates whether this is an isolated incident or an early test for large-scale water contamination.
Deeks goes undercover to obtain information about an infamous arms dealer looking to get back in the business, but the woman he befriends leads the operation in a dangerous directon. Meanwhile, Kensi confronts new emotions as she runs surveillance on Deeks and his female source.
A nuclear explosion in the Pacific reignites the search for stolen nuclear weapons and prompts Hetty to shuffle the NCIS: LA partnerships, sending Callen and Kensi overseas and leaving Sam and Deeks teamed up state side.