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.

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.

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.

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.

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).

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.

The team investigates the brutal murder of a military sergeant found burned in her car, a case Franks suspects could have a connection to the assault of his estranged wife.

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.

Gibbs and Franks investigate the disappearance of a young Marine connected to a mysterious compound with a charismatic leader, and Lala’s fate is revealed.

Still grieving the loss of his wife and daughter, Gibbs helps the team work a case involving a missing girl. The moment that irrevocably changed Gibbs' life is revealed.

The team investigates the death of a famed Marine commander's son, while a pivotal part of Franks' past involving his family is revealed.

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.

The team works the case of an investment advisor found dead shortly after her release from prison. Also, Mary Jo is left reeling by an unexpected development in her personal life.

When the evidence room is broken into and significant cash goes missing, the team looks into a connection to a recent case. Also, Lala opens up to Gibbs, and Kowalski struggles to move forward.

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

Vera receives an unexpected call from Bugs, who claims he's ready to answer more questions from prison after being identified as the sniper known as Sandman.

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.

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.

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.

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.

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.

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.