'Source Code' a gripping thriller with first-rate performances.

In 2009, Duncan Jones directed a brilliant sci-fi mind-bender called “Moon.”

Featuring the vastly underrated Sam Rockwell, this one-man movie didn’t exactly rake in big bucks; but enough folks took notice that Jones -- better known as David Bowie’s son Zowie -- was given the reins on “Source Code,” a big-budget studio film that opened April 1.

A lot more folks will take notice now -- and that’s no April Fool’s joke.

Though not quite as good as “Moon,” “Source Code” is nevertheless a gripping thriller with a dandy script and first-rate performances.

The best thing about “Code” is that in an era plagued by remakes, sequels and superhero retreads, it’s not like any film you’ve ever seen.

The storyline is so unusual that it’s tough to describe -- particularly because another of the film’s strengths is the way it only gradually reveals the truth; and I don’t want to spoil this.

Suffice it to say that Jake Gyllenhaal plays a man involved in a horrific train wreck who later finds out that he was actually placed there -- using a sort of time travel -- to find the bomb and prevent another attack by the same man.

When he fails to stop it the first time, he’s sent back again.  And again.  And again.

And each time he has only eight minutes.

And each time he takes more interest in his fetching young fellow passenger (played by Michelle Monaghan).

“Source Code’s” relentless narrative keys on our ever-increasing desire to 1) figure out what’s going on; 2) see the man succeed on his mission and 3) maybe watch him fall in love as well.

Add to this some unresolved conflict between the man and his father, and you’ve got a film that is utterly enthralling from start to finish.

The ultimate explanation -- as well as the film’s breathless resolution -- is both complex and ridiculous; and tales like this need great performances to keep them from -- if you’ll pardon the pun -- flying off the rails.

Gyllenhaal is both tough and sympathetic; and Monaghan -- given very little to do by the script -- fleshes out a character of enormous warmth and vitality.

Equally excellent are Vera Farmiga (“The Departed,” “Up in the Air”) and the reliable Jeffrey Wright (Leiter in “Casino Royale”) as Gyllenhaal’s superiors.

Together, this quartet lifts “Source Code” well above your average actioner, making it instead a tale of compassion, courage, romance and some very tough decisions.

The film is hampered only by lousy CGI in the crash sequence and metaphysics that spin wildly out of control in the final scenes.

Yet it’s so exciting and engaging that by then you simply will not care.

Nevertheless, one nagging question for those who’ve seen the film:

What the %@*#! happened to the real Sean Fentress?