Having reached the end of his three year contract with Lunar Industries, Sam Bell (played by Sam Rockwell), is anticipating going home. He misses his wife, and his child, and he is starting to see things, and become easily distracted, so much so that he burns his hand beneath a tap by accident. His mental deterioration is, in part, aided by the fact that for three years he has lived on the Moon in the company of a computer called Gerty (voiced by Kevin Spacey) and unable to have live contact with his wife, due to a distortion with the transmitters on the base. Shortly, however, the issues of Sam's declining mental state becomes quite an issue as he, on the way to a harvester, crashes a vehicle and is seriously injured.
Moon skirts a lot of influences and a lot of clichés repeatedly throughout its length. The influence of Kubrick's 2001 is hard to deny, and you'll be forgiven, if in the early part of the film, you accidentally refer to Gerty as Hal. Indeed, a lot the problems that exist in the film surround the computer's presence, as it is required, by sheer sense of not being accused as a rip off of Kubrick's film, to be different to Hal--which of course means that Gerty must be helpful, instead of a hindrance, and must provide the answers to Sam's questions, rather as if it were an electronic God, and a benevolent one at that. At one point, the audience must face the fact that the film would be no longer than fifteen minutes, if Sam had just turned to Gerty, and said, "What's the deal here, Kevin?"
"The company is evil, Sam."
Which is, in essence, what actually happens towards the end of the film.
Yet, still, the film is quite decent, and the one plot device that drives it (conveniently left out so as not to spoil it for you, as it's rather the entire film) allows for Sam Rockwell to do some fine work, and your enjoyment of the film ultimately comes to the question of if you enjoy what he is doing or not. Oh, there's some nice imagery of the Moon itself, though occasionally you might ask yourself why exactly the Moon needs giant harvesters to do its job, just as you may ask yourself the whys and wherefors of various other questions relating to the plot in the film, all of which are not explained to you.
Which, of course, is fine, since the film isn't about that. It's about a man cut off from everything, and what happens when he realises he won't get what he wants. It's moves along at a good speed, it's entertaining, and it's well made, for the most part. Worth the time spent, if you have an interest.