“Primer” deals with time travel, but not in a particularly science-fiction-y way. The science portion is explained, but not in simple enough terms for dumb guys like me to understand. I guess if they explained it TOO clearly, it would either demonstrate how implausible it is, or else it would be SO plausible that everyone would go out and start building their own working time machines, and the movie would lose its novelty.

It is about four men, computer guys, it appears, who wear shirts and ties all the time, even when the ties are loosened and the sleeves are rolled up because they’re sitting around a kitchen table, talking about technical stuff. They’ve developed some kind of product (the movie is not exactly clear on what it is) in the garage, and selling it has turned into a small cottage industry for them.

Two of the men, family man Aaron (Shane Carruth, also the writer and director) and his bachelor friend Abe (David Sullivan), begin private discussions away from the other two, though. They’ve noticed an odd side effect of the whatever-it-is out in the garage, that it seems to be capable of stopping time, at least in a small, confined area. Keeping their research a secret, they expand on the anomaly and soon have de facto time machines in a storage unit outside of town.

The machines are essentially just boxes, possibly owing to the film’s very low budget (reportedly $7,000), but that’s of little importance. As far as I’m concerned, a time machine can be as simple as a phone booth or a DeLorean. What’s unusual about these is how they function. You can’t just choose a time to go to; they can only go backwards, and only in real time. So if you enter the box at noon and sit there for two hours, when you come out, it will be 10 a.m., two hours before you went in. Aaron and Abe use it mostly for day trips, then, waiting until the market closes to see which stocks go up, then going back to that morning so they can buy them.

The paradoxes of time and causality are explored, and if they’d been explored better, the film would have been great. It unfolds intriguingly, revealing information a little at a time, until everything is laid out and we see … well, we’re not sure what we see. An incident at a party involving a gun is referred to, and we gather that there is some desire to go back and try to fix things, but the film eventually becomes too obtuse for its own good, leaving things murky when they ought to have been explained in full. We are left with a fascinating, well-played story that dissolves in the end — a pity, really, since it has so much potential up to that point.

B- (1 hr., 18 min.; PG-13, some profanity.)