AUSTIN - When I saw "Moon" at the Sundance Film Festival, at the very first screening of the film, I thought it was okay.  Not great.  Okay.

I've come to like it more upon revisiting it, but I think of it as a very good first film, someone's announcement more than a totally successful film.  I like Rockwell in it, and that's enough to recommend the film.  And it absolutely made me curious to see what Duncan Jones might do next.  Even if I didn't love the film, I really admired the filmmaking and the ambition.

"Source Code," his second film, deserves to launch him into the ranks of filmmakers who are trusted with big idea popcorn material, smarter than average and populist in its appeal.  It is a slick movie, a "Twilight Zone" style high concept with an ethical question built into it.  Several of them, actually.  And the cast absolutely nails the tone of the material, seeming to confirm that Jones has good taste in actors and he knows how to create a space for them to do great work.  It helps, of course, if you've got actors like Jake Gyllenhaal and Michelle Monaghan, both appealing and demonstrating a real, easy chemistry, essential when you're trying to take this kind of material and invest it with big heart.

You've seen ideas like this before.  A guy wakes up on a train.  He doesn't know where he is or how he got there.  There's a woman across from him, talking to him like she knows him, but he's never seen her before.  He tries to figure out what's going on, tells her that he doesn't know her.  He's upset, agitated, confused.  And just as he starts to get his bearings, the entire train blows up, and everyone onboard is killed.

And then he wakes up, and he's somewhere else.  And very quickly, we learn that he's going to be sent back in to experience the same eight minutes again, and his job is to find the bomb, and then find the bomber.  Why?  Well, that's part of the fun, isn't it?

Gyllenhaal is an entirely sympathetic lead in the film and he makes the process of discovery credible at every turn.  Monaghan has a great character arc, eight minutes at a time, reacting to each new version of Gyllenhaal.  It's a tricky thing, and the script by Ben Ripley makes several very smart decisions.  There's a little bit of scientific set-up, just enough to give you permission to say, "Sure," but it's never overexplained.  Instead, he keeps everything human scale and personal, and it's really sort of wonderful the way Colter Stevens (Gyllenhaal) reaches out to Goodwin (Vera Farmiga) and Christina (Monaghan), two very different women, to help him through what starts as a surreal experiment in time observation, not time travel.  He can't change things, he's told.  All he can do is figure out who the bomber is so they can be stopped before they do anything else.  And watching him test the limitations of his eight-minute excursions is a big part of the fun of the film.  It plays things straight, but with a health sense of humor about it.

Like "The Adjustment Bureau," this film is much sweeter than I would have imagined, and while the entire supporting cast, including Jeffrey Wright, Russell Peters, Michael Arden, and a number of well-cast but largely unknown people, all do a uniformly good job, it comes down to the chemistry between Gyllenhaal and the two ladies, and each of them has such a different presence.  Farmiga is playing a role that is largely her reacting to a camera on her desk, in the same chair, just talking, while Monaghan is the one in the train with him, the one who pushes him to find out if he can, in fact, change what happens on that train after all.

There was some hubbub just before the Q&A for the film, when someone in the theater actually followed Gyllenhaal into a public restroom, then took a picture of him at the urinal.  Gyllenhaal made the guy delete the picture and cops were indeed called to the theater, one of two such incidents I heard about happening tonight at the festival.  Seems like everyone's a little rowdy as SXSW gets underway, but I hope that doesn't ruin the overall experience for the filmmakers, because it played beautifully in the room tonight.  I think "Source Code" is accessible, charming, and breezy, a film that flies by, a movie movie, if you will.  It left me smiling and satisfied, and when the closing credit ran revealing who voices Gyllenhaal's father for an off-camera role, I laughed out loud.  Duncan Jones strikes me as a guy who's built for a long and solid career, a talented but unpretentious director, and with just two movies under his belt, he's already turning into someone you can count on, a welcome addition to the genre ranks.

"Source Code" opens in theaters nationwide on Friday, April 1.