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She fought Ben Linus and outsmarted the Dharma Initiative in a mind-bending Lost, and now plays a tough talking FBI agent battling aliens in V.

So what led Elizabeth Mitchell back into another sci-fi show - albeit one questioning morality, humanity, religion and our innermost fears?

"It really wasn't my intention," she says. "Lost said, 'We don't need you anymore', and I was like, 'Oh, okay'. I thought I would lay low, and I figured I had enough money for a couple of years and we'd be okay."

But the universe had other ideas for the blonde 40-year-old - she was cast as Erica Evans on the remake of V, which is based on the 1984 sci-fi series.

Mitchell is glad the show is a "reimagining" rather than a redo of the original.

"Why redo something that went over so well? I think the script on that whole first miniseries was pretty amazing. It filled in all the blanks and it answered all the questions.

"I'm very comfortable and happy with the reimagining. I'm comfortable with the idea that aliens have landed, and there's a tremendous amount we don't know about them. It feels good to me as a sci-fi fan."

Last year's pilot episodes of V showed a flotilla of alien spaceships arriving on Earth with their curiously telegenic leader Anna saying they came in peace bearing medical and technical advances. Only Mitchell's Agent Evans has discovered their real sinister intentions and has to fight against time to expose their secret, potentially destroying her relationship with her teen son, Tyler who has taken a shine to one of them.

Mitchell's own belief in extraterrestrials might help give her character authenticity. But will V, like Mitchell's last show, take seasons to answer the many questions it presents?

"I think they'll get to [the mythology] a bit quicker," she says. "It will be there if you [want] to seek it out and if it's intriguing to you. If not, you can sit back and eat popcorn and watch the show quite happily.

"Who you can trust along the journey is going to be of tantamount importance," she says. "I loved Juliet [her Lost character] because she was sneaky. You didn't know how much power there was. With Erica, you get a pretty good indication. She's got a fairly massive right hook."

V has been the most physical role Mitchell has played, to date. She's had gun training to look the part of an FBI agent, and often arrives home at night with bloody knuckles. She is even studying Krav Maga - the Israeli martial art - but hopes never to use it.

As well as looking and acting the part, the cast and crew wanted the show to be a special effects extravaganza. The computer wizardry has made V "visually stunning" in Mitchell's opinion but it's the characters and plot she finds the most satisfying.

"I believe the characters are compelling, and I believe we're after something. It's not going to be just us against them. There will be some humans who are truly and completely converted in such a way they don't really care what they're there for. It will be an interesting fight."

With Lost coming to an end, she is relieved fans haven't compared Erica Evans to Juliet Burke - despite playing Juliet in 53 episodes since 2006.

"I am both happy and sad that Lost has come to an end. Happy because I'm an avid reader, and I really do love when my books come to an end. A little sad because it's a whole group of people that I love, and it was sad to see them go their separate ways."

LOWDOWN
Who: Elizabeth Mitchell
What: V
When and where: From Wednesday July 14, 8.30pm, TV2