Jake Gyllenhaal is a helicopter pilot whose last memory is fighting in Afghanistan. When he suddenly wakes up on a Chicago-bound commuter train - in another man's body, no less - he is understandably disoriented, and even more so when the train explodes eight minutes later, warping him into some strange armored capsule where an Air Force officer (Vera Farmiga) communicates with him over a TV screen.
Told that he must be sent back in time and into the body of one of the train's doomed passengers - multiple times if necessary - until he finds out who the bomber is, Gyllenhaal is plunged into a thoroughly entertaining sci fi yarn that is two parts Groundhog Day, one part The Matrix, and several parts old Quantum Leap episodes. (A clever bit of voice casting, revealed only in the end credits, confirms the beloved TV show's influence on the filmmakers.)
Duncan Jones' first feature was the much-lauded Moon, and although that film was written by Nathan Parker (based on a story by Jones) and Source Code's fine script was written by Ben Ripley, both films explore similar themes of identity and free will through the use of repetition and creepy if well-intentioned government plots. In short, as with Moon, Source Code is pure authentic science fiction, though much more action-packed than its predecessor.
Gyllenhaal and the rest of the cast are earnest and believable, and the story keeps you guessing along two fronts: not only about how Gyllenhaal can find the bomb (and the bomber) on the train, but about how exactly he got into this time travel experiment in the first place.
Without giving anything away, the film's one potential flaw is in its conclusion. At first the story seems to close on a poignant - if eccentric - note of grace. Then suddenly it continues for another five minutes, wrapping up a little too tidily. It's not one tenth as disappointing as the infamously protracted ending of Spielberg's A.I., but some may still be annoyed by this coda, which almost feels as though it was tacked on by the studio. Even so, it still offers enough ambiguity to satisfy your smarter-than-average moviegoer.
All in all, I found Source Code a finely crafted and emotionally honest popcorn movie. Worth your time.