Sam Rockwell plays Sam Bell, an astronaut assigned to man a lunar station all alone for three long years, in a future where 70% of the Earth's energy comes from something called "Helium 3" mined on the moon itself. His only company is a computer named Gerty (voiced by Kevin Spacey and an obvious homage to HAL in 2001). And then... something happens.
I'm not going to give away this film's twist, because the surprise is a large part of the fun of watching Moon. I didn't know what was going to happen when I went into the theater, and I'm glad nobody had ruined it for me beforehand. Most other critics are not obeying this principle because the twist happens some thirty minutes in, so they think it's fair game. But trust me: if you like science fiction – and this film is real, authentic science fiction – then just go without any advance knowledge of the story and let yourself be entertained.
Moon isn't a perfect film, but the production design is top-notch, Clint Mansell's score is great, and it's nice to see visual effects (flawless here, by the way) applied to something as modest as our own moon, after enduring a decade of increasingly sparkly superheroes, space battles, and fantasy creatures. Moon leaves a few questions unanswered, but it is still a solid, human, truly unique film. And Sam Rockwell does a fine job. If you're the sort who felt that the sci fi was missing from J.J. Abrams' Star Trek reboot, then Moon will be especially refreshing.