After NCIS fails to locate a mole in the department, Under Secretary of Defense Corbin Duggan insists on new leadership and takes over the Los Angeles unit from Hetty and Granger.
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 saved the life of a lieutenant commander, the NCIS team uncovers his dark past which puts a local teenager in danger. Also, Sam must decide which colleague to take to the Los Angeles football game.
After an NSA analyst is found eaten by a shark, the team's investigation leads them to a cartel's money-laundering scheme and sends Callen into a mental asylum to find a key witness; Kensi struggles with her therapy.
The team's investigation into the electrocution of a college student working on a classified Navy project leads them to his inquisitive daughter, who may be the key to accessing his work.
After Callen’s father, Garrison is found in an NCIS patient’s hospital room during a radiation poisoning case, Callen must take him to the boatshed for interrogation. Also, the team discusses their Thanksgiving plans.
After an unknown female assailant kills two men disguised as Sherriff’s deputies in front of Callen’s home, the NCIS team gets a new lead in the ongoing mole investigation. Also, Nell visits a prison to interview an inmate withholding information on the department’s leak.
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.
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 (Jackson Hurst) returns for Hetty’s resignation.
When a Navy lieutenant and his grandfather are kidnapped from a retirement home, the team's investigation leads them to a con artist couple and the hunt for a rare coin; Callen meanwhile has to deal with his father's actions when he kidnaps the father of his grandson (and Callen's nephew).
Sam resumes an old alias to bring down a major criminal kingpin; Callen and Anna's romantic night is interrupted when they are tasked with escorting a high-value prisoner to Los Angeles for questioning.
After the U.S. Treasury Department is hacked, Nell and Eric go undercover inside a couple's retreat to track a tech-savvy husband and wife linked to the crime. Also, Digital Forensics Specialist Dave Flynn (Scott Grimes) arrives from the NCIS cyber office in San Diego to run ops while Eric and Nell are on assignment.
After an engineer who was developing a new guided missile destroyer is murdered, Callen and Sam go undercover to track his co-worker aboard a plane to Tokyo to sell the classified intel. Also, Deeks plans a surprise get-together for Kensi and her out-of-town friends.
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.
After a highly decorated Navy Captain, Charles Langston, kidnaps a Veterans Affairs administrator who has been siphoning funds, the NCIS team must work with Hetty’s former Vietnam War colleagues, now-retired Admiral AJ Chegwidden and Admiral Sterling Bridges to solve the case.
A gold heist investigation has the NCIS team working with Hetty's former Vietnam War colleagues, Retired Admiral AJ Chegwidden, Admiral Sterling Bridges and Retired Captain Charles Langston.
After Sam's wife, Michelle, is taken from her home, the kidnappers demand the prison release of Tahir Khaled, Sam's arch nemesis, in exchange for information on her whereabouts.
Following the kidnapping of Sam's wife, Michelle Hanna, Sam goes rogue from the NCIS team and attempts to stop his arch nemesis Tahir Khaled from ever targeting his family again.