Rhona Mitra, star of Underworld: Rise of the Lycans, can kick your ass, but fortunately she tends to reserve her ass-kickings for the big screen. Just don't call her Kate. Or Selene.

In Lycans, Mitra is Sonja, a 12th-century vampire who joins forces with her lover, werewolf leader Lucian (Michael Sheen), to battle Viktor (Bill Nighy). Viktor is not only the despotic ruler of the vampires and long the enslaver of the Lycans, but he's also Sonja's father. Rise of the Lycans opens today. Following are edited excerpts our exclusive interview with Mitra.

You are not replacing Kate Beckinsale or her character, Selene, from the first two films, and yet some people seem to think that.

Mitra: It's just that we're both female leads. But they are different characters.

What were the opportunities to be found in doing a prequel, and were there any limitations as a result?

Mitra: Let me think about that. ... No, I don't think there were any limitations. If anything, I think we completely freed ourselves up from all of that by taking it back in time to a completely [new] era. Given that you already have enough poetic license, because the vampire world obviously is pretty much without limits, we did whatever we wanted. I do think there are a few vampire things you have to stick to because people expect them, but other than that we really did have a lot of license.

How satisfying was it to you that within this big action vampire film, your director, Patrick Tatopoulos, allotted time to explore the love story between Sonja and Lucian?

Mitra: I think that was paramount from the beginning. When I went and first had conversations with the folks over at Lakeshore and Patrick himself, that was discussed. Initially, my reaction was, I think, very much like the fans' or the skeptics', or whoever you like, and that was, "I think it's a bad idea to make Underworld III." But when I found out that it was a prequel and that nobody would be filling anyone's shoes and that the focus was on this love story, I thought that was smart.

How did you enjoy working with Bill, Michael and Patrick?

Mitra: Michael had just come off the back of doing Frost/Nixon, and he had packed on quite a few pounds for that. And his character in this had to be incredibly lithe, let's put it like that. That boy worked out and got himself down to such an incredible size, and he really resembles, I think, Jim Morrison now. And that's interesting, because I do think there's a similarity between rock gods and vampires. So it was really wonderful coming to work with his level of dedication and seeing his metamorphosis. And with Bill, it's just pure ease and fun.

And Patrick?

Mitra: Also, Patrick was great. He's a ball of energy and absolutely the most passionate person I think I have ever worked with. And I think the fact that he has been on the front line and was production designer on the first two made his relationship with the whole crew really wonderful. So that's a really big deal, when the director is one of the men on the front line. It creates a balance every day when you come to work.

If this film is a hit, how interested would you be in a sequel to your prequel?

Mitra: Oh, I don't think that would involve me. I think that would be Michael's road.