When you die, the last eight minutes of your life remains electromagnetically imprinted in your brain. If you could inject someone into that persistent time memory and pull them back afterwards, you could send investigators into crises just before they happened and have them identify who committed the crime. It's a fascinating premise for a sci-fi thriller and director Duncan Jones pulls it off splendidly in Source Code.
Air Force chopper pilot Colter Stevens (Jake Gyllenhaal) finds himself in a commuter train heading into Chicago on a sunny Monday morning, chatting with attractive brunette Christine (Michelle Monaghan) who certainly acts as if she knows him. But he has no idea who she is, who he is, where he is and what's going on: his last memories were of flying a helicopter in Afghanistan. Christine refers to Stevens as "Sean" and says he's a school teacher. When he looks in a mirror, he's startled by the unfamiliar face that stares back at him.
Then the train is ripped apart by a bomb that kills everyone on board.
Turns out that Stevens is part of a top-secret military operation called Source Code and, as he gradually learns from his handler Colleen Goodwin (Vera Farmiga), he's going to be sent back to relive the same eight minutes prior to the explosion again and again until he can figure out where the bomb was and who planted it.
There are a lot of sci-fi action films that fall apart by the last reel, films that tax your ability to suspend disbelief until by the end you're just glad to get out of the theater (think of the recent remake of The Day The Earth Stood Still for an example). Source Code holds together remarkably well, with its slick design, constant twists and surprises, and a bad guy who wasn't at all obvious when we try to identify them along with Colonel Stevens. The story makes sense and while the end was a bit melodramatic, it was a satisfying, philosophical ending with a neat twist.