We often hear that casts of long-running television series become a lot like family. When they’re shooting a season, actors spend much more time with their co-workers than they do their own families, which can get kind of rough depending on how happy everyone is on set. If relations are strained between certain parties, or if the series simply isn’t performing up to expectations, that dynamic can easily turn dysfunctional.

Though it hasn’t always been a completely harmonious environment (per Pauley Perrette), the set of CBS’ long-running procedural “NCIS” has largely been free of major drama throughout its 22 seasons. And while actors have come and gone over this time period, some, like Sean Murray and Brian Dietzen, have hung around in one capacity or another for the entire run.

If any one actor served as the backbone to “NCIS,” it was definitely David McCallum. The veteran performer, who rocketed to television stardom in the 1960s as Illya Kuryakin in the NBC spy series “The Man from U.N.C.L.E.,” found a career second wind in 2003 when he was cast as Dr. Donald “Ducky” Mallard, the historian and chief medical examiner of NCIS. McCallum was 70 when he joined the series, and though he aged remarkably well over his time on the show, he eventually had to cut back his workload as he got on in years. He was still considered a series regular when he passed away on September 23, 2025 at the age of 90, which left the cast and crew of “NCIS” mourning the loss of a cherished work family member. So it only felt right to give Ducky a fond, full-episode send-off, which the series did to its fans’ teary-eyed satisfaction.

At the outset of the season 21 episode “The Stories We Leave Behind,” Brian Dietzen’s Dr. Jimmy Palmer discovers that his longtime colleague Ducky died in his sleep. The NCIS team is rocked by this news, but no one takes it harder than Jimmy, who counted Ducky as both a mentor and a dear friend. As everyone moves through the grieving process, Jimmy receives an unexpected visit from a angry teenage girl. This is Serena Zawadski (Olivia Sanabia), the daughter of a slain U.S. Army soldier whose death is being used to boost the election campaign of a shameless politician. Olivia had sought out Ducky’s aid in helping her clear her father’s name, which has become not just an emotional drain but an impediment to her future as she applies to colleges.

Suddenly, the NCIS team has one last mystery to solve with the aid of their beloved Ducky — and they come through for their friend while taking time to share personal remembrances that range from touching to hilarious.

Evidently, everyone who worked on “NCIS” loved McCallum, but, as in the show, Dietzen was particularly close to the actor, which led him to take part in the writing of the farewell episode. McCallum’s death also occasioned a cameo from former star Michael Weatherly, whose beloved Anthony DiNozzo makes a surprise appearance, his first in eight seasons, at the end of the episode.

For the “NCIS” faithful, “The Stories We Leave Behind” was an incredibly worthy goodbye to the great David McCallum. Ducky may be gone, but, as the episode makes clear, he’ll never be forgotten as long as everyone keeps his memory alive via their stories of his kindness, wit and expertise.