In the unexpectedly gripping "Source Code," Jake Gyllenhaal plays an Afghanistan war vet named Colter Stevens who goes from flying helicopters to, next thing he knows, inhabiting the body of a dude riding a commuter train into Chicago. About the time he begins to make sense of his surroundings, an explosion obliterates his train, and Stevens is thrust back into a capsule where he finds he's taking orders on a military project that amounts to bargain-bin time travel. The train blew up that morning, and Stevens is being projected into the last moments of one victim's life, to determine who blew up the train and abort a follow-up attack.
To explain how this macabre replay works, the inventor of the process (Jeffrey Wright) proffers a dusting of confectioner's science — quantum physics! And, uh, stuff! — to keep everyone out of the M. Night Shyamalan gutter. Basically, when someone dies, there's a residue of physical, quantumnal energy that we can plug into, so even though the train has exploded and hundreds of people have been killed, enough of a halo remains that this Source Code thing can send Stevens back to investigate in a dramatic re-enactment. It amounts to an airliner black box crossed with Choose Your Own Adventure, except when Stevens fails to solve the past, the whole shebang goes bang, and he has to return once again.
Once Stevens accepts the disorienting reality, he starts paying a little more attention and stops lollygagging around the doomed train. You'd think he'd be a little more focused on the task at hand — ferreting out the bomber, preventing the next attack, saving the lives of countless Bears fans — but it takes him a while to stop futzing around with the earnest brunette (Michelle Monaghan) across the seat from him. A duty-bound but sympathetic officer (Vera Farmiga) keeps walking him through.
That Stevens dawdles at all, and that he gets incinerated on repeat without completely cracking up, and that the bomber, once found and confronted, blabs more than a Bond villain, and about a dozen other logical potholes all threaten to derail the experience. But these are questions that your brain keeps mostly quiet until you stumble out of the theater after 93 short minutes, because somehow "Source Code" transcends its nonsense. For every five dumb things the script throws in, you find yourself excusing four. Overall it ain't a bad follow-up for director Duncan Jones (aka David Bowie's son), whose mesmerizing feature debut in 2009, "Moon," also tinkered with the concepts of memory and identity. Here he folds a terroristic whodunit into "Groundhog Day."
For his part, Gyllenhaal makes another turn as the sort of action-hero-next-door so common in American cinema during the past decade, since we started shipping non-Stallones and non-Schwarzeneggers to Afghanistan and Iraq, where they also have died, over and over, ostensibly to prevent the next terroristic threat. That the passenger Stevens drops into is a teacher, instead of a cop or retired FBI or similar, only underscores Gyllenhaal's Everyman called to service.
Maybe Gyllenhaal deserves the credit for making this machine go. Or maybe it's the iteration of the film, watching the same scenario unspool in different ways, playing detective along with Stevens as he scratches at his own obscured past. (Why him, anyway?) It's hard to pin down exactly why a movie with this many flaws is this satisfying. Maybe it's just impossible not to admire a good train wreck.