On Monday's episode of CBS' long-running procedural, Harmon's character, Leroy Jethro Gibbs, chose not to take back his badge when the opportunity presented itself. Instead, he decided to stay at the lake and fish, at peace with where he's come following a grueling and intense 18-season ride.
Last night's installment, which marked the turning of a new leaf for NCIS without its leader, was filmed in Bristol Bay, Alaska, over the course of five days, a source exclusively tells ET. The location was chosen because of Harmon's passion to fight to protect its wildlife.
Harmon's departure in the episode was a bit of a surprise, though it had been speculated for months since NCIS was renewed for a 19th season. The desire to keep Harmon's final episode a secret was mainly to keep the audience guessing, and according to the source, Harmon felt it was crucial -- especially with social media -- that any hint of a twist be omitted.
While the 70-year-old actor won't be around the NCIS set on a regular basis, Harmon's Airstream trailer still remains on set in Valencia, California, and he will still be involved in the show as an executive producer. According to the source, the door is still open for Gibbs' return and they are not viewing Monday's episode as a farewell or sendoff to the character.
Even so, Harmon is currently busy working on several other projects he's developing with his Culver City-based production company, Wings Productions.
Following Monday's episode, executive producer and showrunner Steven D. Binder issued a statement regarding Harmon's future on NCIS.
“As an executive producer and dear friend, Mark continues to be an integral part of the fabric of the show. Our north star has always been staying true to our characters, and that truth has always guided the stories we tell and where those characters go," Binder said in a statement. "So regarding the future of Gibbs, as longtime fans of the show may have noticed over the years… never count Leroy Jethro Gibbs out.”
NCIS airs Mondays at 9 p.m. ET/PT on CBS. For more, watch below.