NCIS: Mark Harmon returns as Gibbs – in every episode of Origins season 3

For years, he was the boss on "NCIS": Special Agent Leroy Jethro Gibbs. After actor Mark Harmon left the show, the investigator appeared only a few more times in the hit crime series. But now he's returning. In the third season of the spin-off "Navy CIS: Origins," Harmon will once again take on the role of Gibbs. What makes this special is that it's not a one-time guest appearance – instead, he'll appear in every single episode of the new season.

The return of the popular "NCIS" star was announced in a clip on social media. Alongside the short video, which ends with a shot of Mark Harmon, the caption reads:

"The story he never told enters a new chapter... Mark Harmon will return to NCIS: Origins as Gibbs for all episodes of Season 3."

Here's why Mark Harmon's comeback as Leroy Jethro Gibbs is so special

The spin-off is a prequel to the original series "NCIS," in which Harmon once led the team of investigators who solved a new case week after week. At the center of "NCIS: Origins" is the young Leroy Jethro Gibbs, played by Austin Stowell, who is at the beginning of his career in the early 1990s and is struggling with personal trauma. Even before the recently announced appearances in the upcoming third season, Harmon had already appeared in the spin-off. First, he appeared in the series premiere, and second, he made another guest appearance as part of a later crossover with "NCIS." In addition, Harmon – as Gibbs – can be heard as the series' narrator.

Gibbs' upcoming comeback, however, will be special not only because it means we'll get to see Mark Harmon regularly on screen again for an entire season. His return will also have a massive impact on the series itself – more specifically, on the series' structure. The "NCIS" franchise, which has spawned several spin-offs since its debut in 2003, is typically characterized by self-contained episodes. Once the case of the week is solved, the show moves on to the next one. The third season of "NCIS: Origins," on the other hand, is set to revolve around a case that will be explored in depth throughout the entire season. Specifically, it involves a mystery connected to the older Gibbs of the present – played by Harmon – that also ties into his time at Camp Pendleton in the '90s, as reported by The Hollywood Reporter.

It will be interesting to see how the two time periods are interwoven. However, we'll have to be patient for a little while longer. The third season of "NCIS: Origins" is set to air on CBS this fall.

Mark Harmon is also active behind the scenes on NCIS: Origins

In addition to Austin Stowell as the younger version of Gibbs, the series' cast includes Kyle Schmid as Special Agent Mike Franks, Mariel Molino as Special Agent Cecilia "Lala" Dominguez, Tyla Abercrumbie as Field Operation Support Officer Mary Jo Hayes, Diany Rodriguez as Special Agent Vera Strickland, and Caleb Foote as Special Agent Bernard "Randy" Randolf. "NCIS: Origins" was created by Gina Lucita Monreal and David J. North, who also serve as executive producers – alongside Mark Harmon, among others, who is also involved behind the scenes as an executive producer on the spin-off.

In the original "NCIS" series, Harmon played Gibbs through Season 19. The void he left behind was, in a sense, filled by Gary Cole, who has been on board since Season 19 as Supervisory Special Agent Alden Parker.