What would you do if one morning you woke up in someone else’s body? Would you freak out? Would you run to the mirror to find out if you’re younger or slimmer? Or would search for someone to explain what is going on -- and why? In Source Code, the mind-bending new thriller opening Friday, Jake Gyllenhaal and Michelle Monaghan star in the spring’s first blockbuster. CAHIR O’DOHERTY reviews the big budget flick.

In Source Code, which opens on Friday, April 1, Jake Gyllenhaal plays Colter Stevens, an American soldier who finds himself trapped in a sort of miniature time machine that keeps sending him back to re-live the last eight minutes of another man’s life.

That’s right, another man’s life. Without giving too much away, Stevens discovers that each time he goes back he’s inhabiting the body of an unknown Chicago school teacher on a fast moving train, just minutes before that man is blown to bits in a terrorist attack.

Colter’s mission, we quickly learn, is to find the identity of the person who planted the bomb on the train before another one is detonated. It’s amazing how quickly this wacky set up establishes itself.

Then along comes the charismatic Irish American actress Michelle Monaghan (best known for her turn in the Boston Irish crime drama Gone, Baby Gone) who plays Christina, a character designed to smooth over the rough edges of a script that hurtles along at a breakneck speed.

Some critics have seen elements of Groundhog Day and Christopher Nolan’s Inception at work in this increasingly eerie thriller, but really they’re just being lazy.  The real influence shaping every frame of this taut paranoiac thriller is Alfred Hitchcock, and the aura of intensifying menace is a throwback to Hitchcock’s specialty -- unlikely strangers battling it out on a high-speed train.

Source Code is dark, claustrophobic and weird enough to draw you in and keep you guessing most of the way.  Its ace card is a lovely understated performance by Monaghan, 34, a consistently underrated actress who brings much needed humanity to this otherwise fairly creepy tale.

Yes, that’s right, it may look like a cookie cutter sci-fi thriller, but it must be said that as Source Code progresses and the plot points are revealed, it gets darker and more disturbing, not less so.

It’s fairly edgy material for America’s favorite boyfriend Gyllenhaal, 30, but he’s note perfect in a role the presents a new side to the pec-tastic everyman (if everyman looked as consistently adorable).

On paper Gyllenhaal may be one of the highest paid actors in America, but he’s still one of the most approachable (thanks to careful career guidance by his mom, he says).

But that very approachability has allowed some to take advantage. After a recent screening of Source Code at the SXSW festival in Austin, Texas a photographer attempted to film Gyllenhaal as he used the urinal. For his impertinence the cameraman was body slammed against a wall by the justifiably outraged actor.  So sometimes you have to feel for the nonsense these stars have to contend with.

Having interviewed Gyllenhaal face to face on several occasions now, I can tell you it’s really not an act. He really is considerate, straightforward and smart, and completely devoid of the otherworldly weirdness of more obviously cosseted actors like Tom Cruise, Jonathan Rhys Meyers and Robert Pattinson. That sincerity and straightforwardness serve the film and Gyllenhaal’s performance -- you buy into his confusion and fear, and you root for his escape.

Matching Gyllenhaal up with Monaghan was a canny piece of casting that gives the film all the heart it possesses, and it also goes quite a way to answering the film’s fairly shocking central question -- what would you do if you knew you only had eight minutes left to live?

To a lot of men, spending it in Monaghan’s arms might not seem like a bad decision. Source Code has pretensions to greatness that if never quite pulls off, regardless of the strong performances from the two leads. Ultimately the script just isn’t as intelligent as it suspects it is, although that’s not to say the film isn’t a thrill ride along the way.
As an all around action hero, it’s easy to see what attracted Gyllenhaal to the script, so the real question is what made Monaghan decide to do it?
“I was intrigued the whole way through the movie,” she told the press during an event in Los Angeles. “And the fact that director Duncan Jones was attached to it just brought it to a whole other level.
“I realized what a challenge it would be for an actor to play the same eight minutes over and over again. It really felt daunting but after speaking to Duncan I realized it could be a really cool exercise.”

Having the opportunity to go back to an earlier time to fix what went wrong or to just relive the moment is a powerful impulse that anyone watching the film won’t be able to ignore. Even Monaghan herself admits she was hooked by it.

“I would like to have eight minutes back to explore my wedding all over again,” she says. “That was such a blur and a whirlwind, and I made the mistake of not videotaping it. I kick myself for that decision every day. That’s something I’d like a do-over in. I’d like to re-do that first dance and take some dancing lessons prior to re-doing it.”

Although similar events play out each time Colter travels back for the final eight minutes, there are interesting tonal shifts between each journey. In particular, the deepening understanding and relationship that develops between Colter and Christina gradually intensifies with every repeat trip.

But if that kind of science ever evolved, where it became somehow possible to travel back in time for a re-do, what would be its benefits? For Monaghan it has both attractions and pitfalls. 

“Think of the tragedy that we just saw in Japan. If you had eight minutes to go back and be able to warn people to get to safety. Those are things that we question. Is that something we can do? Is any sacrifice worth that?”

Meanwhile, Monaghan is gearing up for her next release, a drama that sees her changing gears completely and playing to every one of her strengths as a character actress and a leading lady.

“I’m really proud of my next movie,” she says. “It’s a drama based on a true story called Machine Gun Preacher that also stars Gerard Butler, and Michael Shannon plays a preacher who dons a machine gun when he goes over to the Sudan, where he manages to feed and school thousands of children.

“It’s a remarkable story of how one person can make a difference and he does very single day,” says Monaghan.

With things going so well now in her acting career, is Monaghan glad she made all the choices she did?

“I wanted to be a journalist,” she says. “I went to college for four years and then I dropped out and I moved to New York. And that’s when I discovered acting.

“I was living in Chicago and I thought, something is going to happen for me in New York, I don’t know what it is. So I moved there and I was modeling at the time. I was making commercials and acting.”

Monaghan noticed that journalism was the lowest paying degree coming out of college, and realized that would hurt when it came time to repay student loans.

“I had come from a town of 700 people in Iowa. I was really excited about living in a city. So I was suddenly wondering is this really something I wanted to do. I have a real idealistic view of the world.

“But I still love journalism. I still use the journalists’ trick of finding out who, what, when, where and how when I prepare for a role. So in that way I got my money’s worth, but I think I’m in the right career now.”

Michelle Monaghan and Jake Gyllenhaal star in the sci-fi thriller 'Source Code'Google Images