<i>NCIS: Los Angeles</i> NCIS: Los Angeles

NCIS: Los Angeles, one of the most anticipated new dramas of the fall, premieres Tuesday (9/8c, CBS), and every member of the production knows the show has something to prove.

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"My biggest concern, and I think [for] most of us, is to please the current NCIS fans first and foremost, because there's... a huge following," says the show's star, Chris O'Donnell. "If new people tune into the show, that's great, but I feel more pressure to live up to the [original fans'] expectations."

O'Donnell's co-star, LL Cool J, feels similar pressure. "Our job is to do the best work that we can, and depend on [executive producer Shane Brennan] to bring the best stories to the table," he says. "Then we will try to bring those stories to life in a great way.... Obviously, we want to maintain, you know, the current NCIS fan base and all of those people that are joining the show.  We don't want to make them have an allergic reaction to what we are doing on-screen."

See photos of the cast of NCIS: Los Angeles

Whether or not the show wins over the die-hard supporters of the mothership, which also premieres Tuesday, Brennan makes it clear that the new series will be its own animal. But that doesn't mean he won't cherry-pick the elements that make NCIS a success.

"We want to keep it familiar rather than similar, I guess," Brennan says. "What we have on NCIS is a show that's now in its seventh season... and at its core is that wonderful mix of drama, emotion, and humor. For us to attempt to do NCIS: Los Angeles without those three key ingredients would be crazy.

"From that point on, everything else is different," he continues. "We are on the West Coast, it's sunny California, there's a whole different vibe out here.... I think the audience is going to say, yes, this is familiar, but these characters are different and we love them in a very different way. And it's my very strong belief that that's what's going to happen."

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The differences start with the new team's headquarters. The unit has taken over an old Spanish mission because, after Special Agent G. Callen (O'Donnell) was shot in the backdoor pilot episodes, the previous location was believed to be compromised. Brennan says the mission is the perfect place to hide a super-high-tech operation.

"[It's] the very nature of the work that these guys do.  They're undercover," Brennan says. "They're pretending to be someone else. They're living a lie. And so it was always the idea that on the outside you have this old building. On the inside you have this high-tech operations center. So it's a building within a building. It's a building that's undercover."

The team has been in the new digs for about four months, but Callen sees it for the first time in the premiere, as he begins his first official day back on the job after the shooting. But don't expect to get answers as to who pulled the trigger right away.

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"It's four months later, and it's Callen's first day back on the job, and we see his scars.  We literally see his scars," Brennan says. "Will we answer what happened to him and how it happened and why?  In the very best tradition of NCIS, yes, and in the very best tradition of NCIS, you'll just have to wait."

Instead, Callen and Special Agent Sam Hanna (LL Cool J) will work to stop a drug cartel, which they believe is responsible for the kidnapping and murder of one of the boys in white. Fistfights, foot chases, and gunfire ensue. "Obviously, the first episodes that we make, we want to show the audience what we're capable of," Brennan says. "We're flexing our muscle, but we have other stories as well."

Brennan promises some deeper, emotional stories for Callen and Hanna as well, but says the action element will be prevalent all season long. "What you have really with this show is two guys in particular, Sam Hanna and Callen, who work really well together," Brennan says. "There's repartee, a lot of banter, and in the great tradition of those kinds of shows, they tend to get out and kick ass."

Are you excited for the premiere of NCIS: Los Angeles?