SPOILER ALERT! This story contains details from the two-part premiere of NCIS: Origins on CBS.

Leroy Jethro Gibbs’ origin story has finally begun: CBS kicked off its long-awaited prequel to veteran character on Monday NCIS writers-producers Gina Lucita Monreal and David J. North, as well as CBS Studios. And as promised, Mark Harmon returned to both narrate and appear at the fireside writing about his life.

Here, Monreal and North break down the two-part premiere that follows a young Gibbs (Bridge of Spies‘ Austin Stowell) as he begins his career as a newly created special agent at the fledgling NIS Camp Pendleton office.

DEADLINE How much does the average NCIS viewer know about Leroy Gibbs?

GINA LUCITA MONREAL I think it varies, but our hardcore fans know a lot. We’re trying to find a balance between those hardcore fans and hopefully new fans who don’t know anything. That is the line we are walking.

DEADLINE Do they know he failed his psych evaluation?

DAVID J. NORTH No, we just made that up. We’re making this shit up.

DEADLINE That’s what a writer should do. Did they meet his father?

NORTH They met his father at the OG show. His father was played by the great Ralph Waite, who passed away during the run of that series. So we have Robert Taylor playing the younger version of him.

DEADLINE Did you shoot Pendleton?

NORTH We don’t. We talked about it at one point. We did go down there. Gina and I took our writers and went with the director of the two-hour premiere to make sure this was as realistic as possible. We shot in San Pedro to match Pendleton.

DEADLINE Why is it only NIS?

MONREAL Before it became NCIS, it was NIS. There was a restructuring in 1992 and then they changed the name. So it really helps us, even if we just say this is a different time and place. We will play that restructuring within the framework of our show.

TERM Why is Mike Franks (played by Kyle Schmid) considered a legend and how did he get here? He clearly does not fit the classic image of these researchers.

MONREAL That’s a good question that we’re going to answer.

NORTH We know him as a gifted mentor. We know he was a bit of a rule breaker. I don’t know how many episodes Frank was played by Muse Watson on NCIS, but it seemed like a lot was unused. It was exciting for Gina and I because we felt we could dig that character, who the hardcore fanbase knows, a little deeper and find out what would have made this man tick in 1991. The younger version in our show is very different. than the older retired man in the original. Frank is blunt, he tells it like it is. He has a bit of Archie Bunker, but he is someone who has a lot of empathy for the people around him, even if he doesn’t always show it.

MONREAL I would describe him as complex because he does misogynistic things, but he also has another side.

TERM So we see Mark Harmon’s Leroy Gibbs news in the premiere! Did we know he kept a diary?

MONREAL We knew he brought a diary to Alaska.

NORTH Writing Mark’s final episode of NCIS, Gibbs goes to Alaska and when he gets there, he’s looking for someone. He decides that he has found peace there. When we wrote that episode, we didn’t really know what Gibbs would take with him if he knew he was never coming back. One of the things was a diary, because he would be in solitude. That has worked out very well for us here at Origins.

MONREAL David wrote that farewell episode for Gibbs in the original NCIS and did such a beautiful job ending that story. So it’s really nice to see that he can continue that story with our new show.

DEADLINE When we hear from Gibbs’ father in the premiere, he tells his son, “You weren’t built for this job.” What did he mean by that?

NORTH Gibbs joined the Marines at age 18 and was a sniper all his life. He defended his country by hunting the enemy. He was a murderer. Unfortunately, that’s how Jackson sees his son. He didn’t see him as someone who has the patience to do these investigations. I think that every father-son relationship is complex and that fathers do not always see everything that is going on with your son. That is a very difficult moment.

MONREAL Jackson is also a military man. We established in the original show that he flew planes in the military and war. So I think it’s really ingrained in who this family is, because she’s in the military. So it’s shocking for Jackson to see Gibbs make this shift more or less unannounced.

DEADLINE When Gibbs said the phrase “old habits,” he literally sounded like Mark Harmon. You didn’t have Mark do a voiceover, did you?

MONREAL Austin says so. He did a lot of research into the way Mark played this character and incorporated a lot of his mannerisms and his speaking patterns. I think his research and his dedication to this role are very clear.

DEADLINE Are you going to try to match the exact tone of NCIS or do you want this to be a bit more serious?

NORTH We’ll definitely find the humor, but the tone of this show is largely darker. It’s sharper. We’re dealing with some stories that we might not have had in the original NCIS, but we find that even in the darkest moments of loss and grief, humor always rises to the surface.

DEADLINE Will there be a serialized aspect to this?

NORTH It is largely serialized. We have cases every week, but the show really dives deep into character, so it’s a very serialized show.

DEADLINE Is Mark super dear to this character or does he give you a big head start?

NORTH Both. He cares about it so much, but it’s really something interesting. He’s Gibbs and it’s clear that Mark has poured so much of himself into Gibbs over the years. But he really trusts me and Gina. He wants us to fulfill our vision.

DEADLINE How would you describe the NCIS fans? Are they going to keep you on your toes or do you think they’re going to give you a break?

MONREAL Oh, they won’t give us a break and I don’t want them to either. That’s what makes them so great: they’re so invested and they don’t want us to misunderstand this, and we certainly don’t want to misunderstand this. We love and respect our fans and we want to do this right for them. We’re so excited for them to see it.

DEADLINE What differences will we see in the way this team investigates cases compared to the way the modern team operates?

NORTH Forensic investigation takes a long time. Even fingerprints can take six months. So it’s much more of a dirty, conventional, old-fashioned way of researching, which from a writer’s perspective is great. It can be challenging because you don’t have the crutches to just say, “Oh, okay, we’ll go through the fingerprint analysis and find our guy.” It makes us go back and look at the characters and use our agents and their skills to solve these cases.

DEADLINE Will we see Mark sitting by the fire again and writing in his diary? Or do you put it somewhere else?

NORTH Everything is possible. We don’t want to reveal too much about what will happen and a lot is still being figured out. Our show focuses on 1991 and these characters, this rich tapestry that we have with these characters, but anything is certainly possible.

DEADLINE Young Gibbs is a handsome man. Do you see him considering a romance or is that not in the plans for now because he is still so damaged?

NORTH I think you said it. This is a human being and he has suffered a lot of loss, but romance is certainly not out of the question.