There’s something to be said for a movie written, directed, scored, edited, produced by and starring the same guy. Shane Carruth made Primer for $7000, surely less than a day’s catering on a Tom Cruise picture. I became interested when I read an A/V Club piece that named it the most scientifically accurate film about time travel.

Carruth is a former engineer, and the emotional tone of the film is in keeping with any number of engineer jokes you’ve heard. At the same time, the narrative is dense and challenging – Carruth has real potential as a storyteller. He takes things a step beyond “show, don’t tell,” and allows the audience to just observe. You will probably miss several things the first time around – the movie runs a brisk 77 minutes but I spent a couple of hours figuring it out later (and there remains some welcome ambiguity, plus a killer joke at the end.) Very little is explained, and some of that comes from an unreliable narrator. (I didn’t figure out which character did the voiceover until much later.)

Here’s the story: Four smart guys get together after their day jobs to work on side projects that will hopefully become marketable. They had a previous invention stolen, which provides motivation beyond what is immediately apparent. Their latest attempt is a device that temporarily reduces mass. It seems to work, with an unexpected side effect: items in the device appear to spend more time inside than has passed on the outside. (Carruth doesn’t simplify any of this for the lowest common attention span – some will find it exhilarating and others impenetrable. There are many bloggers who have developed diagrams and explanations about the film which are useful study aids. Don’t consult them ahead of time.)

It’s refreshing that Carruth doesn’t have his characters interact with any real historical events, or anything of obvious consequence. They can only travel several hours (so it seems at first) back in time, and the person inside the device subjectively experiences that same amount of time inside – it’s no DeLorean. They identify stocks that did well during the day, then go back and buy them in the morning. Every complication comes from character-based motivation. The real interest for the viewer is in piecing together not just what happened, but why.

The obvious forebear of Primer (great title, with several packed meanings) is Christopher Nolan’s Memento. Carruth is less interested in plot mechanics than Nolan – at heart, he’s an ethicist more interested in questions than pat answers. See this movie (streaming on Netflix). Come for some great science fiction, stay for the metaphysics.