When the team's trusted K-9 agent, Gary Callahan, is critically wounded at a crime scene, NIS races to track down the culprit while a surprising pre-Pendleton chapter in Franks' life is revealed.

When the murder of Pedro Hernandez is unearthed, Gibbs faces a reckoning. But when he needs his team most, the loyalty of one is brought into question.

Young Ducky is sent to Camp Pendleton to shadow the team while they work a case and, in the process, he reconnects with Gibbs after the two crossed paths years earlier.

With the Camp Pendleton office in danger of being shut down, the team confronts an uncertain future.

When Dr. Tango is arrested for stealing human remains from a national park, Dr. Donald "Ducky" Mallard returns to assist the team in proving his innocence.

As Leroy Jethro Gibbs prepares for his first Christmas without his wife and daughter, flashbacks reveal the unlikely journey that led to his first day on the job as a special agent.

The case of a missing woman who disappeared after a night of clubbing with a Navy seaman takes the team to Mexico, where they learn of a possible connection to Gibbs' past.

After the shocking developments in the Sandman case, the team works with the FBI to investigate further; while Wheeler struggles to hold onto his job, his family reaches a crisis point.

When a marine captain shows up at Camp Pendleton exhibiting symptoms of a fatal virus, NIS goes on lockdown and Gibbs is forced to take charge. As panic spreads, the team races to determine whether it really is a deadly outbreak or something else entirely.

Tensions rise when Franks’ estranged older brother, Mason, blows into town, desperate for help after hitting rock bottom. Also, the team investigates the robbery of a Navy bank while Lala, still struggling after her accident, makes a decision about her future.

Gibbs and the NIS team investigate the small-town death of a naval officer, but struggle to come up with justice. The crossover continues on NCIS S23E05 Now and Then (II).

Gibbs starts his career as a newly minted special agent at the fledgling NCIS Camp Pendleton office, where he forges his place on a gritty ragtag team.

Gibbs and the gritty ragtag team continue their investigation at the fledgling NCIS Camp Pendleton office.

The team investigates the murder of a Marine who had recently been handpicked for a classified mission. Also, Wheeler’s personal life is upended, Lala is thrown by unexpected news from Vera, and Gibbs and Diane double-date with Randy and his wife.

While Gibbs and Lala grow closer on a case, Gibbs’ long-distance relationship with Diane is further tested by the arrival of an unexpected guest.

NIS investigates the murder of a dementia-afflicted Jane Doe. Also, flashbacks reveal the first time Gibbs met Franks

Gibbs goes undercover for the first time with Lala as NIS works the case of a dead Navy seaman who may have been sharing top-secret intel that poses a threat to national security. Also, Lala struggles with her place on the team and an unexpected development in her personal life.

A murder near Camp Pendleton leads Gibbs and the team to a suburban mall in San Diego, where Gibbs takes matters into his own hands. Jackson Gibbs pays Franks an unexpected visit.

Gibbs and the team investigate the case of a Navy priest who was killed in the confessional booth and may have been targeted by mistake. Meanwhile, Randy shows Gibbs the ropes of working a protective detail while struggling with a personal situation.

When the body of a college swimmer washes up on the beach, the team must determine if it was an accident or murder. Also, Gibbs prepares for his first interrogation.

With the countdown on to an execution, Franks races to extricate the location of a missing body from a death row inmate and honor a promise he made to the victim's sister before time runs out.

The team investigates the brutal murder of a veteran who fell on hard times after serving in Vietnam, leading Franks to reflect on his own struggles following the war. Also, Gibbs considers a new path forward.