The story follows Sam a man working on the moon harvesting energy for earth. You learn that he has 2 weeks to go before his three year contract is up. He goes out to one of the harvesters but is distracted by a hallucination and crashes into the harvester. The next scene is of Sam in the infirmary. He wakes up but is to curious for his own good and disregards orders to stay in the base and leaves to investigate his crash site, where upon arrival discovers a body still in the car. He takes the bod home and soon realizes it’s himself, or a clone of himself. When the first Sam wakes up they both start to question there existence and both learn they are just clones of the original Sam Bell. They both find future Sam clones and find out what happened to past Clone Sam. Near the end of the movie First Sam calls his wife and finds out that she is dead and that his infant daughter is really fifteen now. After coming to terms that he is not really Sam and that he is dying he help Second Sam to go to earth.
The movie had an interesting way of showing clones. They explain that not all Clones are the same. They develop differently and are essentially different people. They only consistency among the clones are that they look the same and are implants with the same memories. The movie shows homage to previous movies such as blade runner and 2001 Space Odyssey. For example Gerty the robot in Moon is like the one in the Space Odyssey, except much nicer and not evil.