At an unspecified time in the future, the Earth is overpopulated and polluted. On the third moon of Saturn, an aging scientist named Adam works on hydroponics experiments to help feed the people of Earth. He is aided by his nubile, young assistant, Alex, with whom he also shares an intimate relationship as they are the only two people in the compound. On a large spacecraft approaching Saturn, Captain James is called to the shuttle craft launch pad for immediate departure. James rushes to his locker to get his equipment when crewman Benson comes into the locker room. James has heard that Benson failed his “mental test” and was found potentially unstable, but comments he, too, would have been mentally unstable if he had known he was being assigned to Saturn 3. Without speaking, Benson fastens a safety belt around his waist and opens an emergency hatch which sucks James directly into space, killing him. Closing the hatch, Benson takes the equipment, goes to the launch pad, and departs in the shuttlecraft, while the spacecraft’s crew remain unaware than Benson has taken James’ place. Once on the moon, Adam and Alex show Benson around the Saturn Three Experimental Food Research Station, where they have been working for the past three years. Benson tells them their research is behind schedule and he is there to help. Soon after, the moon goes into “eclipse,” meaning its rotation will take them behind the planet Saturn. Because they are “shadow locked,” they will not be able to communicate with Earth for twenty-two days. When Alex tells Benson she had never been to Earth, he replies the last time he was on Earth, the pollution there hurt his lungs. Nonetheless, Alex longs to know what it is like to go outside and breathe the air. Benson says he will take a blue-colored pill known as a “blue dreamer” to help him sleep and gives some to Alex for her future use. Since Alex has never heard of the drug, Benson warns her the pill also causes heightened sensory experiences. Benson asks to have sex with Alex, but she declines explaining she is exclusively with Adam. Benson says on Earth, it is considered rude to be in a monogamous sexual relationship. Later, Benson watches on the station’s monitors as Adam and Alex have sex. The next day, Benson begins assembling a robot, the first in the new “Demi-god” series, which will be furbished with actual human brain tissue. Benson reports it will take three to four weeks to complete the robot, after which time either Adam or Alex will be obsolete. Later, Adam overhears Benson again ask Alex for sex and becomes angry. He confesses to Alex that he wishes he could “flush” both Benson and his robot into space. Later, Alex and Adam take a “blue dreamer” pill and have passionate sex. About three weeks later, the robot is complete and Benson injects fluid into its brain tissue. He then introduces Alex and Adam to the eight-foot-tall robot which he has named “Hector.” When Benson instructs Hector to bring them a flask from the table, Hector accidently crushes it with his hand. Benson admits the robot needs more fine-tuning. Later, Benson connects a small radio antenna to a receptacle at the back of his neck and Hector begins replicating Benson’s every body movement. Sometime later, Hector and Adam play chess while Benson explains how he performed the “brain drain” to program the robot. Later, Benson programs Hector to fixate on Alex and dislike Adam. Benson asks Hector why he is communicating by typing rather than talking. Hector replies he is not yet ready to talk, then types in the words “murder” and “killer.” Knowing those words are about him, Benson instructs the robot to delete that information from his memory banks. Later that night, Alex hears her dog, Sally, crying, and rushes to the hydroponics laboratory, only to find Sally dead and Hector nearby. The robot grabs Alex’s hand, but she hits an alarm with the other hand, which Hector then grabs. Adam and Benson get to the laboratory, but Hector will not follow Benson’s commands. However, Hector puts Alex down when she asks him herself. Benson explains since the robot was programmed with his brain, Hector likes Alex as much as he does. Just then, Hector causes a beam to collapse on Benson and Adam then causes another beam to collapse on Hector. He rescues Benson, then locks Hector in the laboratory. On a monitor, the three observe Hector tearing apart the door, but see his power draining. When Hector goes to recharge his battery, Adam sends a strong charge of electricity which causes Hector to collapse. Adam orders Benson to dismantle Hector, but once that job is complete, the other robotic devices in the compound reassemble Hector. Meanwhile, Benson barges into Adam’s quarters, saying he is leaving and taking Alex with him. Adam grabs Benson’s neck and chokes him until he loses consciousness. However, Benson comes to quickly and hits Adam in the head. With Adam blacked out, Benson drags Alex through the compound, but Hector comes to her rescue, cutting off both of Benson’s hands. Adam comes to and plans to escape in Benson’s shuttlecraft. Adam tries to freeze Hector with liquid nitrogen, but that only slows him down momentarily. Adam sets a trap and Hector falls into a pool of water in the laboratory. As Adam and Alex rush to the shuttlecraft, Hector causes it to explode before they can get in. The two return to the compound and lock themselves in the communication room, only to hear Benson tell them that he’s come to an agreement with Hector. Since the couple thought Benson was dead, they are confused by the message, but nonetheless go to meet him, only to find that Hector is imitating the deceased captain’s voice. Adam and Alex are knocked unconscious, but awaken just as the moon comes out of the eclipse. A small spaceship with two pilots makes radio contact to check on the station. Suddenly, the couple hears their voices talking to the pilots and realizes Hector is imitating their voices as well. Satisfied they are safe, the ship says it will return in six months to check on them. The couple worries about their fate, trapped in the station with Hector. Soon, Hector gives Alex and Adam chores to perform. When Adam confronts the robot, saying he is in charge of the station, Hector refuses to obey. Holding an explosive device, Adam lunges at Hector and the two fall into the water just as the device explodes. Hector breaks into hundreds of pieces, but Adam is also killed. Shortly after, Alex takes a transport ship to Earth.