DEA agent Talia Del Campo turns to the NCIS: Los Angeles team for help after her partner is murdered. Also, after Kensi grows suspicious that Deeks is hiding something, he surprises her by introducing her to his mother.

Deeks is arrested and interrogated in connection with the murder of his former partner, while the team tries to prove his innocence.

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 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.

Season 9 begins with Hetty turning in retirement papers and disappearing. A new executive director arrives and immediately makes staffing changes. Meanwhile, Sam, still mourning his wife’s death, insists that Callen find a new partner.

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.

The NCIS team investigates the home invasion of Navy Captain Dean Hadlow, who was entertaining his friend, General Omer Abidi of Pakistan, when robbers successfully stole money, jewelry and highly classified information. Also, Deeks and Kensi interview candidates to manage the bar.

After the chief of logistics for a naval weapons station collapses on the job, the NCIS team must determine if this is a terror threat or a stress-induced breakdown. Also, Kensi and Deeks research different honeymoon locations.

The NCIS team investigates the murder of a journalist who was writing an exposé on a mishandled classified military operation. Also, as their wedding day quickly approaches, Kensi and Deeks work on the last remaining items on their to-do list.

After months of planning, the NCIS family celebrates the wedding of Kensi and Deeks. Also, an old acquaintance, Anatoli Kirkin, pays Deeks a surprise visit on his wedding day and he isn’t alone.

After a rise in deaths caused by black market opioid use, the NCIS team links the street drug to funding for terrorist activities

NCIS is called to investigate when a woman is seen fleeing the scene of her husband's murder. Also, Roberta Deeks comes into town to meet Rosa, and Sam looks for another aide for his father.

When a Marine falls ill during a training mission due to an attack by a genetic weapon, the NCIS must track down the person responsible for unleashing it. Also, Deeks struggles with balancing work and home life when Rosa comes down with the flu.

The NCIS team continues the case with ATF and the stolen weapons. Also, Callen and Anna decide on an impromptu wedding.