Episode 1 : Deep Trouble, Pt. 2
Callen and Sam are trapped in an armed submarine that terrorists have aimed to hit an aircraft carrier in San Diego. Meanwhile, Hetty defies orders and forgoes her trip to Washington, as the team tries to locate and save Callen and Sam and prevent the terrorist attack.
Episode 2 : Inelegant Heart
The NCIS: LA team discovers that one of their own is compromised when they investigate the murder of a Navy contractor involved in illegal transactions of confidential data. Meanwhile, Hetty is under investigation in Washington, D.C., when the Department of Justice arrives in L.A. to investigate the team.
Episode 3 : Praesidium
The NCIS: LA team takes action to protect one of their own while being interrogated by the Department of Justice. Meanwhile, Nell goes undercover as Hetty, and Director Leon Vance gives Hetty disturbing news while she is in Washington.
Episode 4 : The 3rd Choir
When the NCIS: LA team learns that someone from their past is targeting one of their own, they desperately search the city. Meanwhile, Operational Psychologist Nate Getz visits Nell to help her through her traumatic experience. Peter Cambor and Gerald McRaney guest star.
Episode 5 : Black Budget
Callen and Sam head to Mexico to track down the only employee who managed to escape a professional shooting at the Department of Defense. Meanwhile, the rest of the team works to uncover the motive behind the shooting. Bill Malone and John Billingsley guest star.
Episode 6 : Seal Hunter
When Sam is arrested for murdering a woman, Callen and Granger work to clear his name. Meanwhile, Kensi and Deeks discover a link between the victim and a student from Sam's past. Anderson Silva guest stars.
Episode 7 : Leipei
When a man is murdered by a small drone, the team discovers his connection to a terrorist group that is planning another local attack. With time running short, Nell must use her drone expertise to try to divert a disaster in Long Beach.
Episode 8 : The Grey Man
Kensi and Deeks go undercover to investigate the murder of a homeless man who was a former marine and CIA agent and discover his connection to the Mexican cartel.
Episode 9 : Traitor
After Granger is poisoned by the mole and Eric is one of the seven suspects, Hetty orders a lockdown while everyone is investigated.
Episode 10 : Reign Fall
Sam reflects on his own upbringing and relationship with his father when the team investigates the murders of marines who have sons in military academies.
Episode 11 : Humbug
The team investigates a burglary at a cyber-security company, but Callen must steer clear of the crime scene after Hetty reveals his girlfriend, Joelle, is one of the lead witnesses. Also, the team discusses their personal holiday travel plans.
Episode 12 : Spiral
While Callen is undercover in the mail room of an office building to investigate an arms dealer, it is taken over by terrorists and Callen becomes a hostage. When the team arrives to help, they discover the entire building is wired with explosives.
Episode 19 : Blaze of Glory
When a missile test is hijacked and sent off course, the team searches for the hacking group responsible for the attack with the help of a young computer specialist Hetty brings in to assist the team. Also, Nell sees the bond between the tech guru and Eric and she becomes jealous.