"I've had to learn how to fight," she says of her preparations for the role. I've had to learn how to use a gun and I've had to learn how to speak Russian. I've had a lot of really interesting experiences already. "The fighting's great," she continues. "I was absolutely terrified when I realised it was not a stunt double, it was actually me doing this. This was something I'd never done before. Once I got past the initial shock I was frighteningly so into it - I was like, 'OK, who's next - bring them on! Let's go!'"

Ryan joined Dark Skies mid-way through the first season, as producers hoped that Juliet's exotic background and seemingly cold, enigmatic presence would add an extra dimension to NBC's Saturday night UFO conspiracy show. For her part, Ryan fought desperately for the role - and not just because she was seeking stable employment.

Although, when she first appears, Juliet seems to be some what one-dimensional, subsequent episodes deliver a number of surprising revelations - including her husband's fate while on a mission to recover a crashed UFO, and her encounter with a Gray as a child in Gorky Park, which resulted in her abduction by the aliens. ''You find out what makes Juliet tick, explains Ryan. "When you first see her she's this very tough, very skilled mercenary agent who is capable of killing or disarming somebody. As the episodes progress you see that she can kill but she doesn't relish doing it. She doesn't do it with a cold heart, and you see why she does what she does." Ryan was born in Munich, Germany and spent her formative years as an ''army brat," travelling across the world. I was raised all over. [I'd lived in] Kansas, Hawaii, Georgia, Texas and Kentucky, by the time I was eleven, she reveals.

Had she always wanted to be an actress?

Yeah, definitely,' is her positive response. "No question. I always wanted to be an actress - most of the time an actress or something else. So when I was little I went through the 'actress or a veterinarian' period, when I was in high school I didn't know if I was going to major in theatre or biomedical engineering. And of course my practical nature won, and I decided to major in theatre! I've always wanted to do this, so it really is a dream come true."

''You'll find that lots of actors are army brats," she explains. "That's because you need to learn to be the new kid in school and play a different role to fit in. When you're a child and going through the moving, it's tough, but as an adult, I realise it taught me to be adaptable." She graduated from Northwestern University as a National Merit Scholar with a BS in theatre, and moved to Los Angeles to pursue roles in television and films.

In early roles she played "Mostly the sweet young thing," making guest appearances on Melrose Place, Mat lock, Murder She Wrote, The Flash, Who's The Boss, Reasonable Doubts and Diagnosis Murder. Last year Ryan made the move into films, working on two small independent movies over the summer. The first was The Last Man ("a very funny script: it's about the last three people on Earth"); the other was Men Cry Bullets.

Home is in Chicago, which she shares with her investment banker husband. This means living in Los Angeles on weekdays, and returning to Chicago at weekends. Ryan likes this routine, claiming it allows her to distance herself from Tinseltown, and recognises the advantages of being married to someone who is not in the entertainment business. "My husband is someone who's in the real world. It's a big help that I don't have both feet in Hollywood."

Doesn't this weekly commuting ever prove wearing?

"It doesn't help a lot," she replies candidly. "It's tough. My husband and I have had a commuter marriage our entire marriage, with the exception of the one year I was pregnant and stayed home. But apart from that we've always been apart, except at weekends, and in the summers I'll go home for a month or two, or in December when things slow down here. But the bulk of our time is spent apart, and it is hard, but my agent understands that if she needs me for an audition I will fly back at a moment's notice, and that's not a big deal. My husband travels a lot with his job, so we have a lot of frequent flyer miles so we can hop on a plane with no notice. That's a nice luxury and he is very supportive, which is very important.

My son is a commuter as well - he's grown up his entire life on planes. He spends part of his time with me, and part of his time at home. My mom is the nanny and she flies back and forth with him, which is a huge help, but the hardest thing I've ever had to do is leave my son in Chicago and come out here:" Ryan claims that joining the Dark Skies ensemble mid-way through the first season reminded her of school days, when she was always the new kid on the block.

When asked to recount her first impressions of the series, the actress reveals that she was drawn to the unusual premise.

''It's basically about the 'what ifs in history," she muses. "What if aliens really had landed in Roswell in 1947? What if the government knew about it and covered it up?" Like The X-Files before it, this mixture of alien visitations and government conspiracies in Dark Skies has made the show essential viewing for an army of fans. While underlining that she loves the series, Ryan admits that she doesn't buy into the current fascination for the unexplained. 'There's a lot of evidence to believe it, so it is very interesting, but I'm just not sure I believe it all," she says. "There are a lot of people who take it a little more seriously than maybe it should. There is a very large chunk of our population who firmly believe in extra-terrestrials."

So does the actress believe in the existence of alien life herself?

"It might be arrogant to think that we're the only living creations in all of the solar systems that there are," she responds. "Space is so vast... We haven't done such a great job, so I don't know why God couldn't have started over somewhere else. I don't necessarily believe in aliens coming to the States, and I don't buy into the government cover-up - I think that's a little bit paranoid."

"[Dark Skies] is fantasy, it's fun, it's television - it's supposed to be entertainment. It's not supposed to be a documentary, and I don't think any of us look at it that way. We love our jobs, but I don't think any of us look at it as though we're doing a huge public service by getting this information out! This is not some huge government leak about aliens to the public because we're going to find something out... it's an escape."

"I think the more stressful our times get, the more we look for fantasy escapes."