<i>NCIS</i> NCIS

Rena Sofer isn't having a hard time keeping her character's secrets on her guest stint on NCIS.

That's because, according to the 24 and Heroes vet, she doesn't know what those secrets are.

Rena Sofer lands at NCIS

Sofer's run on the show involves the investigation of a Navy pilot's death. Aerospace engineer Victor Tillman (guest star Marcus Giamatti

) and his prototype jet packs become the focus of the investigation. But before Gibbs (Mark Harmon) and his team can get any answers from Tillman, they have to go through his hard-nosed attorney, played by Sofer."She's a high-priced lawyer, and she's not afraid of anybody," Sofer says of her character, Margaret Allison Hart. That includes Gibbs, against whom she holds some sort of mysterious grudge that even Sofer doesn't fully understand. "When I did the episode, I had a lot of questions and no one really answered anything for me," Sofer says. "That's the way they like to do things over there. I don't know what she's after or why. I don't know if she hates Gibbs or what. It actually makes it fun for me that I don't know why I'm saying a line that I'm saying."

Watch a preview for the next NCIS episode, "Ignition"

McGee (Sean Murray), who leads the investigation, also inherits some of Hart's ill will toward Gibbs. "I basically put McGee in his place," Sofer says. "In my very first scene, I make it clear that I know [he's] talking to me, but I don't have time for him and I don't really care what he has to say."But the scene is really about the fact that even though I am talking to McGee, I'm really looking at Gibbs," Sofer continues. "I think she takes this case to make herself known to Gibbs more than anything else. It's her entry into his world."

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It won't be a one-time visit to GibbsLand, either. Sofer confirms that she will be back for at least one more episode, which is shooting now. However long Sofer's stay on NCIS lasts, she says the second half of the season is shaping up to be a crowd-pleaser. "There's a clear motion being set by NCIS," she says. "We have no idea what that motion is based on what we've done, but it's very mysterious and it's very intriguing. And if it's intriguing to the actors playing the roles, then I can't even imagine how exciting it's going to be for the viewers."NCIS returns Tuesday at 8/7c on CBS.