the plot: Aaron (Carruth) and Abe (Sullivan) and their two friends spend their off-hours working on a mysterious invention in Aaron's garage. As they progress, they realize they've built something unique-possibly the "most important thing any living being has ever witnessed." It's a time machine, one that actually works, and as Aaron and Abe discuss its possibilities, they gradually ostracize their partners from the work. Soon, the two are gallavanting into the near future to get stock tips to use in the past. But what starts as a simple money-making scheme gets complicated. It seems that future versions of Aaron and Abe are also coming back into the past. There are other problems, too. The two men start experiencing physical side effects from their temporal journeying, such as bleeding ears and deteriorating motor skills. As the experiment spirals out of control, Aaron and Abe both realize they've been lying to each other-there's more than one time machine, and an outsider has discovered their secret.

why it's good: Primer is first-class science-fiction, with the emphasis on science. Carruth and Sullivan speak techno-babble in hushed tones throughout the movie; you may feel a little bad for not understanding what they're saying, but it's OK-the characters barely understand it themselves. That kind of ambiguity is one of Primer's strengths. Carruth has made the story just plausible enough, the science just detailed enough, that it all seems real without being hokey or contrived. The film's multi-layered story, with its cyclical narrative and subtly surprising twists, will give viewers who stick with the movie the reward of a fierce mental workout. Also notable is the fact that first-time filmmaker Carruth wrote, directed, produced, scored and acted in the film, which was completed for around $7,000. It's a simple, understated and, at 80 minutes, a surprisingly short film, yet it never looks or feels low budget. In fact, when the paradoxes and time travel shenanigans reach their peak, the movie feels downright epic.

why you should own it: Primer is fresh out on DVD, which is probably the best way to view it, just so you can jump back and forth between scenes and figure out what's going on. The disc features commentary by Carruth and the rest of the cast/crew. If clever, brain-bending films are your bag, Primer is definitely worth owning.