Mark Harmon on Returning to ‘NCIS: Origins’ After Choosing to Leave Franchise — and Why His Son Isn’t Portraying Young Gibbs in Prequel!!!!!

After 18 years of playing the special agent on “NCIS,” Harmon exited the show as a series regular in 2021 but remained a series regular. However, he was never far away — he cared too much to fully put it in his rearview mirror. So much so, when his son brought him the idea of a prequel, the two went directly to showrunners David J. North and Gina Lucita Monreal to get it off the ground.

“Is there a story to tell? Definitely. Is it going to be different than people know? Definitely. I couldn’t be more thrilled with Gina and David, who they represent and their history with his show,” he says of “NCIS: Origins,” the prequel set to debut on Oct. 14. “They were the best I ever worked with on that show, and I love what they’ve done and what they’ve worked very hard at and tried to push toward. My job is to try to protect that.”

It hasn’t been an easy journey, Harmon says, but he’s happy to enjoy the calm now ahead of the series premiere.

“It’s going to be hard work, and you know there are going to be changes. You know that there will be things you can control, and things you’re going to have to fight for, and things you can’t control,” he says. “Right now, it feels like we fought for every bit of it but it feels good.”

The show picks up in Camp Pendleton in 1991, shortly after the murder of Gibbs’ wife and child. Austin Stowell will portray a young Gibbs — a role once played by Harmon’s son, Sean Harmon, on seven episodes of “NCIS.” For the prequel, Sean serves as an executive producer.

“He’s an actor, writer, producer a surfer, he does a lot of things. You have to come to decisions about what you want to do in life, or what you think’s important. I just think he made a choice and had to make a decision in some ways,” Harmon says of why his son didn’t step back into the role. “He likes executive producing.”

As for Mark Harmon, he’s made himself completely available on set for any questions the cast has — and he knows there will be, since he played the role for so long. Since he fully trusts the show and the team behind it, he wasn’t hesitant to re-enter that world.

“Gina and David had asked me to do the voiceover, and that was always part of my understanding. I don’t know if it was clear initially, how that was going to take place,” he tells Variety. “Then the question was, after that, how are you going to do that? Is he standing there with his finger on his chin? Is he writing a book?”

Harmon will appear in the first episode, but any details about how are being kept under wraps. “That was intended to be a surprise,” Harmon quips of the cameo; North shared the news during a panel last month.

Either way, Harmon just wants everyone to keep loving life on set — which has been the case so far.

“There’s got to be changes. That’s life, right? Everybody’s working hard, and everybody’s got a great attitude and then this will be on the air, and it’s going to get judged. That judgment will change some things,” he says. “But our job is to do the work and try to really, even from the creation of the next episode, we’re constantly trying to keep the bar at a certain level.”

“NCIS: Origins” premieres on CBS Monday, Oct. 14, at 9 p.m. ET.