The movie takes place in the futuristic world were all energy on earth is harvested from the far side of the moon. The main characters are astronaut Sam Bell and his robot companion Gerty. The movie shows the astroanut Sam Bell do his routinely duties in the far side of the moon which include monoriting the robots that extract Helium-3. Sam is responsible for collecting Helium-3 from the harvesting robots and send it back to earth(Harvesters). He is the only human on the moon and is about to reach the end his 3 year contratc with the company that is responsible for supplying the energy source, Lunar Industries.
His chronic communication problems have disabled his live connection from Earth and are only able to communitcate through the occasional recorded messages from his wife Tess, who was pregnant with their daughter Eve when he left. His only companion is an artificial intelligence named Gerty, Gerty assists him with the base’s automation and provides comfort for him.
Two weeks before the end of his contract, Sam begins to suffer from hallucinations of what could be his wife and of a bearded man. A halluciantion distracts him while recovering a helium-3 canister from a harvester, causing him to crash his rover into the harvester. Sam falls unconscious and awakes in the base infirmary with no memory of the accident, he overhears Gerty having what appears to be a live chat with Lunar Industries managers. Lunar Industries then orders Sam to remain on base and informs him that a rescue team will arrive to repair the harvester.
Sam being suspicious he sabotages a gas tube in order to persuade Gerty to let him outside. He travels to the crashed rover, where he finds his unconscious doppelganger. He brings the double back to the base and tends to his injuries. The two Sams start to wonder if one is a clone of the other. After a heated argument and a fight, Gerty reveals that they are both clones of the original Sam Bell. Gerty activated the newest clone after the rover crash, and convinced him that he was at the beginning of his three-year contract, Gerty later confirms that his memories of his wife & daughter are implanted.
The two Sams search the area finding a communication jamming stations, the older Sam goes back to base and discovers a secret vault containing hundreds of unactivated clones. They determine that Lunar Industries is unethically using clones of the original Sam Bell to avoid the cost of training and transporting new astronauts, as well as deliberately jamming the live feed in order to prevent the clones from contacting Earth. It also reveiled that clones who believe they’re about the end their contract are incinerated just before their “final return to Earth”. The older Sam drives past the interference radius and tries to call Tess on Earth, he instead talks with Eve who is now 15 years old, she reveils that Tess died some years ago. He hangs up when Eve tells her father (Possibly the original Sam Bell) that someone is calling. Gerty helps the older Sam access the recorded logs of past Sam clones, showing them get sick as their contract expires which reveals that the clones are designed to ‘break down’. The older Sam appears to be sick, a sign that he is about to “Break down”.
The two Sams realise that the incoming rescue team will kill them both if they are found together. The newer Sam convinces GERTY to wake another clone he plans to leave the awakened clone in the crashed rover and send the older Sam to Earth, but the older Sam, having learned that the clones are designed to ‘break down’ at the end of the 3-year contract, knows that he will not live much longer. He suggest that he should be brought back to the crash site and that the newer Sam to go back to Earth.
Following Gerty’s advice, the newer Sam reboots Gerty to wipe its records of the events. Before leaving, the newer Sam reprograms a harvester to crash and wreck the jamming antennas, enabling live communications with Earth. The older Sam, back in the crashed rover, remains conscious enough and watches the launch of the transport carrying the newer Sam to Earth. The rescue team is fooled after finding a newly awakened clone in the medical bay and the corpse of the older Sam inside the crashed rover. The helium transport arrives at Earth, and over the film’s credits, news reports describe how Sam’s testimony on Lunar Industries’ activities has stirred up an enormous controversy, and the company’s unethical practices have plummeted the company’s stock