While being carefully monitored by the Under Secretary of the Navy due to the identification of a mole in their department, the team lands an important case involving a Syrian terrorist.
A short-staffed NCIS team tackles an abduction case while Hetty is held in Washington, D.C., and another team member remains in the ICU.
A Triad assassin poisons a Homeland Security agent; the discovery of a warehouse of counterfeit purses reveals a money trail to stolen government funds; Nell joins the team in the field.
The murder of a Navy machinist sends the team on a citywide hunt for evidence; Anna Kolcheck (Bar Paly) partners with Callen and Sam in the on-going mole investigation.
A maintenance worker with a dark history puts a local teenager in danger; Sam has to choose which of his colleagues he'll take to the football game.
Callen poses as a patient in a mental health facility to find an NSA agent who vanished while tracking an ISIS cell that was attempting to cross the Mexican border.
An attack on a graduate student working on a new electromagnetic weapon for the Navy is linked to international warfare; Kensi struggles with physical therapy for her spinal injury.
Callen must interrogate his father after he is found in a patient's hospital room during a radiation poisoning case; members of the team discusses their plans for Thanksgiving.
The team gets a new lead in the mole investigation after an unknown assailant kills two men disguised as sheriff's deputies in front of Callen's home; Nell interviews a prison inmate who has information on the department's leak.
NCIS looks into the disappearance of a Navy lieutenant commander who is working on foreign cyber threats with the NSA; the team celebrates the holidays.
After a Navy reservist is killed protecting a city councilman, Sam goes under cover in a private security firm that has links to criminal organizations.
Callen, Sam, Granger and Deeks get arrested as the result of planted evidence on the day Under Secretary Duggan arrives for Hetty's resignation.
When Hetty goes rogue, she leaves the NCIS team completely in the dark; the mole kidnaps one of the agents.
An NCIS agent is held at an unknown location and tortured by the mole, and another agent discovers he was betrayed by someone he least expected.
While investigating the kidnapping of a retirement home resident, the NCIS team discovers a pair of con artists who go from home to home scamming the elderly out of their money; Callen confronts his father on his illegal activity.
Sam assumes a former alias in a risky undercover operation to take down an elusive drug lord; Hetty interrupts Callen and Anna's romantic night to assign them a mission to escort a prisoner.
Nell and Eric go under cover to track a tech-savvy husband and wife linked to the hacking of the U.S. Treasury Department; a digital forensics specialist arrives from the NCIS cyber office in San Diego to run operations in Eric and Nell's absence.
Callen and Sam go under cover to track an engineer attempting to sell classified information; Deeks plans a surprise for Kensi and her friends.
The team investigates when a defense contractor designing a nuclear attack weapon is suspected, by her husband, of selling Navy secrets to a foreign government.
The NCIS team must work with Hetty's former Vietnam War colleagues after a highly decorated Navy captain kidnaps a Veterans Affairs administrator who has been siphoning funds.
The NCIS team works with Hetty's former Vietnam War colleagues, A.J. Chegwidden, Sterling Bridges and Charles Langston, on a gold heist investigation.
When Sam's wife, Michelle, is taken from her home, the kidnappers demand that Sam's arch nemesis, Tahir Khaled, be released from prison in exchange for Michelle's whereabouts.