After a biological disaster destroys civilization, a lone scientific outpost buried under the Mojave Desert struggles to survive. Their food supply is dwindling, forcing scientists, John and Michael, to hunt for food. At the base, David and Sue attempt to convince their superior, Hal, that they must abandon the station and walk eighteen hundred miles to their sister base in the Rocky Mountains, when they receive a distress call from John saying he and Michael are being attack by mutant humans with heads resembling crocodiles, known as “Gargoyles.” Hal orders Sue and David to assist the hunting team. Taking Buster, the outpost’s dog, they find the two men lying dead near a human encampment. David radios that he found the team, as well as another ten bodies with their intestines ripped out. Linda, the station doctor, convinces Hal they must study the bodies as they have lived exposed to the disease and must have developed a resistance to it. Hal orders Andre, a maintenance man, to accompany Linda to collect samples, but he refuses to go. David hears a rockslide and he and Buster go to investigate. When Buster spots Karen, a young survivor of the human settlement, running away from a gargoyle, he gives chase, until David blows a dog whistle. The gargoyle screams and runs off. David and Sue bring Karen back to the base, unaware they are being followed by gargoyles. Not long after sealing the outer hatch, the mutants destroy all the surface security cameras. Below ground, Linda announces to Hal that Karen is three months pregnant. Hal orders her to keep this a secret in case they have to terminate the pregnancy if the fetus shows signs that it is a mutant. The next day, David gets a rare radio message from the Rocky Mountain laboratory stating they are under gargoyle attack, then the signal goes dead. Linda informs Hal that Karen has gone from being three months pregnant to eight months overnight. After briefing the crew, Hal orders the fetus removed, but, if possible, kept alive so it can be studied. During the operation, Linda reaches into the uterus only to have the fetus grab her hand. It then tears through Karen’s abdomen, scurries across the floor, and escapes into an air vent. Sue calculates that if the creature maintains the growth rate of the gestation period, it will be full-sized in twenty-four hours. Needing more weapons, Neil rigs up a portable power pack to turn the surgical lasers into a ray gun. However, it uses so much energy it can only fire four times before it is out of power. Andre turns welding equipment into a flame thrower. Hal splits the men into two teams. The women protest at being left behind, but Hal fears they will be raped, like Karen. David, Buster and Andre head for the second level with the flame thrower and a crossbow. As David turns a corner, the gargoyle attacks Andre from behind, slitting his throat with its claws. David runs back to find the creature gone. As he bends over Andre’s body, the monster leaps from the air vent and attacks. Buster leaps on the gargoyle, forcing it to run away with the dog chasing it. David blows the dog whistle, causing the gargoyle to scream and leap into a vent. David finds Buster seriously injured. Watching the monitors, Sue sees the attack and runs out of the room before Linda can stop her. On the floor below, Hal and Neil receive a radio transmission from Linda stating she is in trouble and they rush to an elevator. When it opens, they find the creature. Before Hal can react, it grabs Neil and the elevator doors slam shut. Sue and David call for the elevator, but when it arrives they find Neil’s dead body and the gargoyle. Before they can react, the creature grabs Sue and the elevator doors slam shut. Linda rushes down to help and they meet up with Hal. The three go down another level and find the creature raping Sue. Hal empties his ray gun into the creature as Linda and David drag Sue to safety. The wounded creature charges Hal and rips him to pieces. After patching up Sue and Butch, Linda tells David that Sue is pregnant and asks if it could be his. David admits it could be, but Sue insists she was not pregnant before the gargoyle raped her and insists on an abortion. Linda refuses to abort the pregnancy until they are sure it is not human. Later, Linda and David return to sickbay to find Sue dead from performing an abortion on herself. An autopsy proves a gargoyle fetus was growing inside her. After examining the fetus, Linda declares that its hearing range is higher than humans and realizes David’s dog whistle must cause them pain. They make a tape of the whistle and play it over the intercom as David hunts him on the lower levels. The whistle noise causes the creature unbearable pain and as it thrashes about, it tears off an electric wire that starts a fire. Linda attempts to activate the sprinklers, not noticing the dog whistle tape has broken. David finds the fire and uses a fire extinguisher to fight it. The creature attacks him, so David drops the extinguisher and shoots the gargoyle with a crossbow. The monster yanks the arrow from its chest, then leaps on David. Hearing David’s screams over her headset, Linda sees the whistle tape broken, splices it, re-threads it, and gets it playing again. David crawls into a supply room where he fashions a spear with his knife, duct tape and a length of pipe. He stabs the creature as it attacks, but it rips out the knife and knocks him across the room. Linda appears and distracts the creature by hitting it with a pipe, allowing David to get Andre’s welding flame thrower and to set the monster ablaze. Convinced the gargoyle is dead, Linda helps the wounded David down the hall to the elevators. However, the creature regenerates its broken and burned body and goes after them. They barricade themselves in a closet and David hands Linda his whistle. She crawls through an air vent back into the hall, yells at the creature and jumps back into the vent. She leads the creature into an air shaft, but drops the whistle. As the creature crawls up to her, she strips two wires, but there is no electricity. Meanwhile, David crawls into the elevator, gets to the control room, and activates the electricity to the lower levels. Linda zaps the monster with wires. It falls down the shaft onto a fiber air filter suspended above a huge fan. The creature panics and its toes tear the fiber, causing it to fall into the slashing blades of the fan and get dismembered. Linda returns to the control room in time to hear a radio message from the Rocky Mountain Laboratory saying they are alive. The next day, Linda, David and Buster emerge from the underground laboratory armed with a tape machine playing the dog whistle. From a safe distance, they watch as gargoyles enter the shelter. David uses a remote control to blow it up. They begin the long walk to the Rocky Mountain outpost.