Mark Harmon is approaching a milestone few longtime NCIS fans can believe.

On September 2, the actor who made Leroy Jethro Gibbs one of television’s most recognizable characters will turn 75 years old.

But Harmon isn’t simply celebrating his birthday and looking back at the past.

He’s getting ready to become Gibbs again.

After stepping away as a regular on NCIS in 2021, Harmon remained connected to the franchise behind the scenes. He became an executive producer and narrator of NCIS: Origins, which follows a younger Gibbs during his early years at Camp Pendleton.

Now that’s about to change in a big way.

CBS has officially confirmed that Harmon will appear onscreen as the older Gibbs in every episode of Season 3 of NCIS: Origins.

And this isn’t expected to be a collection of quick cameos.

Present-day Gibbs will be at the center of a new mystery connected to events from his past, with the story unfolding throughout the entire season.

For fans who spent nearly two decades watching Harmon lead the original NCIS, it’s the kind of comeback many weren’t sure they would ever see.

Harmon has made occasional appearances since leaving the flagship series, but Season 3 will put the older Gibbs back into an ongoing storyline.

The new season premieres October 6 on CBS.

So as Harmon prepares to turn 75, he isn’t riding quietly into retirement.

Instead, one of television’s most beloved special agents is preparing for another mystery.

And for longtime NCIS viewers, seeing Gibbs back on their screens week after week might be the best birthday surprise of all.