Mostly gibberish, but fairly compelling gibberish, at least until the plot ends and there’s still a half hour left in the movie. Valuable lesson, though: if you’re gonna base your film’s central time-travel conceit (or time re-assignment, rather) upon a bunch of ridiculous technobabble, it’s a wise move to have Jeffrey Wright be the guy to spout off all this mumbo jumbo. Especially if he’s sporting a limp and a crutch.

I’m impressed with how up-front Duncan Jones is with the finality of the situation—your protagonist is dead and no one on that train’s getting out alive, so suck on that, moviegoers—but ultimately Jones and writer Ben Ripley want to have their cake and eat it too. If your hero’s narrative arc is based upon the premise he wants to be allowed to die after he completes his mission—noble considering his dramatic, imioned line on how a soldier should only have to give his life once for his country—it seems a bit of a cop-out to provide him both an honorable death and a new life with his sweet new gal-pal. Hard to be stirred by a sacrifice that ends with your protagonist enjoying a swell afternoon making goofy faces into the Cloud Gate at Millennium Park. Undercuts those stakes just a little bit.

Not to mention the moral issues the plot conveniently sidesteps. First off, in that final reality where Captain Colter Stevens (Jake “Hollywood’s Go-To Hero with a Haunted Past" Gyllenhaal) gets resurrected via quantum mechanic jibjabbery, what happens to the real Sean Fentress? Does he die? Is he just erased from existence altogether? Does he find his consciousness trapped in his own body while Stevens takes over the controls? Shit, that’s less like a happy ending and more like the beginning to a Spike Jonze-directed psychological horror film.

Also, every time Stevens goes back and reassigns some time, he creates a new alternate reality separate from the one where Dr. Rutledge (Wright) and Capt. Goodwin (Vera Farmiga) are bossing him around. And every time he fails, the train blows up in this new reality, and the authorities are left with no clues to find the dirty bomb about to take out Chicago and kill two million people. So does that mean the good guys—Wright and Goodwin—are creating a new universe where millions of people are killed each time their little experiment goes awry? Stevens screws the pooch at least a dozen times. So do our heroes, in actuality, create a dozen new realities where two million Chicagoans die each time Stevens fails? That means Wright and Goodwin kill 24,000,000 people in their quest to stop that nuke. That’s not heroic. That’s Doctor Doom-level villainy right there.

But, in the end, you’re not supposed to put too much thought into Source Code, so I guess it works as a mild diversion, at least until the bad guy is stopped and the movie sputters on for a painful fourth act. (Call me crazy, but if some random dude stands up on a train and starts telling everyone about how his girlfriend is desperately trying to get him off of her during sex, that’s not a standup routine, it’s a reason to alert the authorities.) Still, the leads are great—no other actor’s eyes convey emotional distress quite like Mr. Gyllenhaal’s—and the plot remains twisty enough to subdue those nagging questions until three seconds into the closing credits.