Kensi and Deeks go undercover at a decommissioned nuclear power plant where a Gunnery Sergeant moonlighting as a security guard was poisoned by radiation.
The team investigates the murder of a tech entrepreneur turned venture capitalist who secretly developed a computer program that allows for undetectable data collection.
In order to locate Arkady in Russia, the NCIS team goes undercover with his daughter, Anna, at a gala in Los Angeles to gain access to the Russian Consul General's computer. Part one of two.
After extensive surveillance footage of Sam's family is found in Africa, Sam and Callen fly there to determine who is responsible and for what purpose. Also, Sam's family is moved from their home to a safe house. Ella Thomas guest stars.
Callen and the team try to save a child in imminent danger who has been brainwashed by a terrorist cell. Also, Deeks and Kensi discuss having children.
After Operational Psychologist Nate Getz (Peter Cambor) fails to check in with Hetty while working undercover on a mission linking organized crime to terrorism, the team learns he is working with an infamous crime leader.
As Granger escorts Jennifer Kim (Malese Jow) back to Los Angeles, he interrogates her regarding a North Korean spy and she admits to knowing he is her father.
Sam and Callen go undercover as firefighters when top secret information about suspected terrorists is stolen from a secure Department of Defense container at the site of a fire.
Sam receives a distress code from his son that his school has been taken over by a group of extremists, so the team heads to San Francisco to save the hostages.
The team travels to Syria to capture a high-value target, but the mission goes awry when their chopper is shot down, leaving Kensi badly injured and the rest of the OSP team must work around Duggan to ensure they get out alive.
The NCIS LA team investigates an abduction case while down two members, with Hetty being held in D.C. for questioning, and another still in the ICU following the mission in Syria.
After a Homeland Security agent is poisoned by a notorious Triad assassin, NCIS uncovers a warehouse of counterfeit purses and a money trail to stolen government funds. Also, Nell joins the team in the field.
The murder of a navy machinist with high security clearance sends the team on a city-wide hunt tracking evidence. Also, Anna Kolcheck partners with Callen, and Sam assists Hetty in the on-going mole investigation.
After a maintenance man saves a lieutenant commander's life, the team discovers his dark past that places a local teenager in peril. In the meantime, Sam must decide who to take to the football game.
Callen is forced to interrogate his father when he's found in an NCIS patient's hospital during a radiation poisoning case. In the meantime, the team discusses their plans for Thanksgiving.
The team gets a new lead in the ongoing mole investigation when two men disguised as Sheriff's deputies are killed in front of Callen's home. Meanwhile, Nell visits a prison inmate who's withholding information about the department leak.
The team celebrates the holidays as they investigate the disappearance of a Navy Lieutenant Commander who's working with the NSA on foreign cyber threats.
