Moon opens with an advertorial that informs us that the moon has been identified as a huge source of energy for Earth, and that "friendly" big corporations are doing their best to provide us with reliable pure energy.

It seems one of these energy production centres on the far side of the moon is staffed by a lone maintenance guy named Sam Bell, who is at the tail end of a three year contract. His only companionship is a computer called Gerty who is sorta like the mechanical arms from Iron Man, only he has Kevin Spacey's voice.

As Sam is all by his lonesome, he fills his time with hobbies, exercising, TV, tending to his garden and waiting for dispatches from employers and his family on Earth, which are delayed as the far side of the moon gets no live signals due to inaccessibility. His only action is when one of the many "harvesting" machines is experiencing malfunctions or needs maintenance.

On one of these call outs things don't go according to plan, and Sam wakes up afterwards in an infirmary