Astronaut Sam Bell (Sam Rockwell) is nearing the end of his three year contract of harvesting Helium-3, a precious energy source, from the far side of the moon. Since his only communication with earth is through the use of pre-recorded messages, and his only assistant a computer named GERTY (voiced by Kevin Spacey), isolation begins to take an alarming toll on his mind, mere weeks before he is to return home. This sets into motion a series of events which reveals the terrible truth behind his mission.