Now, she co-stars alongside Jake Gyllenhaal in the mind-bending thriller "Source Code," and once again she's front and center in the action. Under the direction of Duncan Jones ("Moon," son of Bowie), "Code" follows Colter, a solider (Gyllenhaal) sent on board a train that will blow up eight minutes after he arrives, and using some cool gadgetry, is able to relive the events final eight minutes to uncover the cause.

We talked to the enthusiastic Monaghan after the South by Southwest premiere of "Source Code" about wrapping her brain around the twisty plot and what it was like reliving the same eight minutes everyday with Jake Gyllenhaal.

What was it like sitting in a theater full of excited audience members during the premiere for "Source Code?"
I've seen the movie, but never with an audience. It changes everything. When you see the audience really respond to the action, the emotion, the humor -- it makes you feel so proud. I felt so excited for Duncan, because he had such a warm reception here for "Moon" a few years ago, and to be asked back, to be part of that and on the receiving end was really special.

The movie replays one sequence over and over, each time changing tiny details and geography. Was it confusing reading the script on how that was going to work?
We really broke it down. It was one of those movies where you had to technically know what was going on. Everyone had to be on the same page and it was something that's potentially a continuity nightmare [laughs]. Personally, I understood it, I grasped it, I bought into it and then I separated my part, the source code. I thought, 'OK, I'll leave Jake and Vera over here, do their thing, and I'm going to concentrate on these eight minutes and nuance them.' I wanted to create subtle changes so we could keep it engaging.

How were you able to incorporate new elements into each variation of the source code?
That was really the daunting thing. I initially thought, 'Oh my God, this is going to be so boring, why am I doing this?' But then I realized that's the challenge. We have to do something different. So then it was going in and totally trying to change it. The initial source code I wanted her to be mysterious, a little Hitchcocky. And we sort of tried to achieve that -- different source codes...through body posture, voice. Duncan and I kind of made a little road map on where I wanted to take each source code, and we were in total sync. Jake, Duncan and I would be huddled for half an hour going, 'OK, source code number three. So now what?'

Since each source code is only eight minutes long, you only have that chunk of time to develop your character Christina. Did you end up developing a background for her?
Absolutely. I was on the 8:20 Dekalb train to Chicago every morning. I was a commuter. I was a paralegal. I wasn't really living my life to the fullest potential. And that's thematic, it's about living your life to the fullest. You strike up a conversation with strangers every now and then and share parts of your life and someone gives you a fresh perspective. This was all the stuff I created in my background and one day I just started sharing with this guy.

The movie could have been a very serious sci-fi thriller, but ends up having a good deal of comedy in it. Was that always the goal?
You know, I think... it's all due to Jake. He's great in his performance because it's not outwardly 'ha ha' funny, but a lot of things in his body language... he's a really physical guy. He can say a lot in a twitch or a blink. And as the movie goes on it lends itself to moments of levity, because by then it's a movie that knows it's a movie, and Duncan had great instincts about the comedy.

What's next for you?
I've got a film coming out called "Machine Gun Preacher" with Gerard Butler, Michael Shannon, [director] Marc Forster, it's really good, I'm very proud of it. It's based on a true story and it's going to move people. And this summer I'm going to do an independent called "Better Living Through Chemistry" with Jeremy Renner.

Any more sci-fi, genre projects in the works?
Maybe. A few things. I'm producing things at the moment, developing them. It's kind of a like a "Bourne Supremacy" meets "Run Lola Run" for a girl.

Sounds like lots of butt-kicking.
Oh yeah!