After napalm is detected at a crime scene, the NCIS team investigates the sole casualty for possible links to terrorism.

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.

The NCIS team tracks a highly skilled assailant determined to avenge her father's death by killing a Brazilian diplomat.

Callen and the team question CIA Agent Joelle Taylor's backstory after she escapes from a kidnapping and turns to Callen for help.

The team must find assailants who illegally crossed the border and attacked California Highway Patrol officers; Homeland Security sends Nell's older and bossy sister to assist with the case.

Kensi is transported to a missile launch facility to help thwart a takeover of nuclear weapons.

LAPD Detective Whiting calls in a favor when Deeks' former partner goes rogue.

Sam goes undercover as a day trader after a prominent investment banker with ties to a Russian oligarch is murdered. Meanwhile, one of Callen’s aliases is the victim of credit card theft, and Mosley is concerned it signals something bigger.

After weapons with a $1 million street value are stolen, the team tracks the evidence to a wealthy charity event, prompting Mosley to be added to the guest list with Callen and Sam as her security detail.

During the murder investigation of a Navy Lieutenant on leave in Los Angeles, the NCIS team uncovers classified surveillance briefs she smuggled into the city that may have been sold to a foreign buyer.