Mark Harmon on His Unlikely Path to Best-Selling Author and Revisiting Gibbs With ‘NCIS: Origins’

Mark Harmon keeps finding surprising avenues for himself, as he is now a best-selling author — despite zero intention of ever becoming one.

The performer, who starred on CBS’ NCIS as lead special agent Leroy Jethro Gibbs before saying goodbye in season 19, is still focused on telling stories about the U.S. Navy. After he and former NCIS special advisor Leon Carroll Jr. co-wrote last year’s best-selling nonfiction book Ghosts of Honolulu, centering on the attack on Pearl Harbor, the pair are back with Ghosts of Panama. Now available, the new book explores the U.S. invasion of Panama in late 1989 and how the Naval Investigative Service special agents investigating the murder of a young U.S. Marine helped change the course of history.

During an interview with The Hollywood Reporter, Harmon explains why he turned down an offer to write a book about NCIS; how Carroll’s personal experience helped inform their writing about Panama; his reaction to being asked to shoot promos for prequel series NCIS: Origins (which he narrates and produces); whether he feels conflicted about leaving NCIS; and what it was like to return as Jamie Lee Curtis‘ partner in the forthcoming movie sequel to Freaky Friday. (For more stories about NCIS, check out THR’s in-depth oral history of the show.)

How did you first get involved with writing Navy-focused nonfiction?

In the very beginning, I was asked if I was interested in doing a book on the TV show, and I had said no. When I first joined the show, part of what they sold me on was that this was all going to be based on real cases. But pretty soon, it settles into murder-a-week because that’s television, right? The idea to do this book in the first place was: If we can tell the real history of this agency, then I’m interested, and I’m interested if Leon Carroll — whom I met 20 years ago as a technical advisor on the show — is with me on this. That’s what we did in the first book, and we jumped off with a World War II story and the early formation of what became NIS.

What led you to the topic of Panama for this latest one?

For the second book, Panama was always on our possible list. The cool thing about this is, Leon was in Panama [with the military] during this time. So that story then becomes first-person, whereas the story we did before on Honolulu, that’s really about research narrative because all those people are dead. I have no real desire to be a writer, to be honest with you. But I do think there are certainly stories to tell, and there’s a lot of them. I also think that if we don’t pay attention to history, generally things repeat themselves. (Laughs.)

What is the writing process like for you and Leon?

We just talk, and we talk about different people. With Panama, Leon’s own recollect from the agents who were there at the time, and his part of the story while he was there, opens up certain doors. In a weird way, maybe because of this TV show, people can talk about it a little more. These special agents, they’re basically spies and do a really difficult job.

Has there been a possibility of adapting the books for the screen?

I’ve been asked that a lot. I don’t know. I’m just kind of locked in at the moment of trying to find good stories to tell, and I don’t know what the barometer is for that. I listen to ideas or thoughts or a piece of history. We’ve already got an angle on a third that I’m really excited about, but I haven’t committed to it yet. I find it a little unbelievable that people are interested in the books, which they obviously have been.

When you say that there was a pitch for you to write about the show itself, what would that have looked like for a book?

I don’t know what they were talking about, but I wasn’t interested in doing that. There’s a big difference between the real of it and then what Hollywood does. I’m thrilled the show has been as successful as it’s been. The first day on the show, we worked 22 hours, so that wasn’t exactly what I had in mind. There were a lot of changes in those first three or four years. People don’t realize that, but this show didn’t jump out. It wasn’t a hit from the minute we did it, at all. You’re reintroduced to that now in doing this Origins show that I’m involved with. Right now, you’re hoping for the backend pickup. That’s as long as your focus is. And you’re doing that because you have a crew that are concerned about their jobs.

Given the books that you work on now, it seems that Gibbs has been such a core part of your life.

I was sent the NCIS script, and I just know that I read the name “Leroy Jethro Gibbs,” and the name stopped me. People say, “What attracted you to the story?” I said, “The name.” (Laughs.) There’s more to it than that, obviously, but I didn’t expect to be taken in like I was. That’s also a credit to storytelling and thinking you have something to potentially offer that role.

Is there a part of you that wishes you were still doing NCIS?

I actually don’t think like that. I was with the show a long time, and I don’t know anybody who thinks in terms of, “Hey, I’m going to do a pilot, and it’s going to last 20 years.” That’s unheard of. But this show, obviously, has been successful through a number of different forms. This Origins thing is really a period piece. It’s 1990, back when it was NIS. So that’s been historically interesting for me to be learning about the agency in a different way than I had in the past. And looking at it in a different way, too, as an executive producer.

Austin [Stowell’s] playing that character now, not me. In the beginning, they had me doing promos together with him. I said, “I get it, but this is your thing. I’m not in front of the camera.” (Laughs.) I’m excited about this cast, and yet you look at it now, and you know things are going to change. They always change.

Speaking of which, I imagine there are still fans who have trouble wrapping their heads around Sasha Alexander’s death at the end of NCIS season two.

And that happened for a very specific reason. That was an actor’s choice to leave the show and then a creative choice to do it a certain way. Then people go, “Wow, that really shocked me.” It’s like, “Well, good, I guess. Right?” Because people are talking about it, and yet, is that something that’s normally done? No, but then that’s also the reason you try to be part of those. You try to catch onto a few of those in a career. And if they work, great. If they don’t work, then we wouldn’t be talking about it.

What was it like to return for the Freaky Friday sequel, Freakier Friday?

It’s comfortable with Jamie and always has been. I’ve known her since she was 15 or 16. Obviously, it’s a different story now, and yet I enjoy time with her. When you look at the long form of life, you’re talking about moments with people and sharing them and being with people you liked being with. That’s always been true about her for me, so I was pleased to do that.