Under Secretary of Defense Corbin Duggan takes over the NCIS Los Angeles unit when they fail to find a mole.

The Naval Criminal Investigation Service's Office of Special Projects takes on the undercover work and the hard to crack cases in LA. Key agents are G. Callen and Sam Hanna, streets kids risen through the ranks.

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 goes undercover as a patient in a mental hospital to find an NSA agent who vanished while pursuing an ISIS attempting to cross the border.

When a graduate student developing an electromagnetic weapon for the Navy is attacked, the team uncovers a link to international warfare.

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.

After a Navy reservist is killed while protecting a city councilman, Sam is sent undercover in a private security firm with links to several criminal organizations. Also, Callen and Anna discuss the next steps in their relationship.

The mole has once again compromised the NCIS team as planted evidence results in the arrests of Callen, Sam, Granger and Deeks, on the day Under Secretary Duggan returns for Hetty's resignation.

Hetty goes rogue and an agent is kidnapped by the mole.

One agent is held in an unknown location and being tortured by the mole, while another is betrayed by someone unexpected.

After a retirement home resident is kidnapped, the NCIS team uncovers a pair of con artists: Ginger and Edward O'Boyle, who hop from home to home scamming the elderly out of their money. Also, Callen confronts his father on his illegal activity and the danger it places on their family. Written by CBS

Sam assumes a former alias in a risky undercover operation to take down an elusive drug lord. Also, Hetty interrupts Callen and Anna's romantic night to assign them a prisoner escort mission.

Nell and Eric go undercover at a couple's retreat when the Treasury Department is hacked and the crime is linked to a tech-savvy husband and wife.

Sam and Callen board a flight to Tokyo posing as businessmen to trail an engineer trying to sell schematics for a missile destroyer.

The NCIS team investigates a defense contractor, Rebecca Larmont, designing a nuclear attack weapon after her estranged husband, Victor Larmont, says he has proof she is selling Navy secrets to a foreign government. Also, Kensi goes undercover as a professional dancer at the Cuban club where the husband works, while Deeks is undercover as the bathroom attendant. Written by CBS

Hetty's old colleagues from the Vietnam War partner with the team when a Navy Captain kidnaps a corrupt Veterans Affairs administrator.

The team works with Hetty's old Vietnam War colleagues on a gold heist investigation.

After Sam's wife, Michelle (Aunjanue Ellis), is taken from her home, the kidnappers demand the prison release of Tahir Khaled (Anslem Richardson), Sam's arch nemesis, in exchange for information on her whereabouts.

Sam Hanna goes rogue from the NCIS team in an attempt to stop Tahir Khaled from ever targeting his family again.