Handymen Valentine McKee and Earl Bassett build a fence in the desert. On the way to another job, they encounter Rhonda LeBeck, a college graduate student monitoring seismographic activity. She asks if anyone has been drilling or blasting in the area, because she is getting “strange” readings. Valentine and Earl promise to look into it. They drive to the town of Perfection, Nevada, population fourteen, and stop at Walter Chang's Market for beers. Survivalists Burt and Heather Gummer pick up supplies for their nearby house-bunker. In the desert, as Rhonda LeBeck packs gear into her truck, the seismograph needle jiggles and something moves beneath the ground, but she drives away. Elsewhere, Valentine and Earl bury garbage with a bulldozer, then drive to another job cleaning a cesspool with a septic pump. As the contents splatter all over them, Valentine suggests to Earl that they need to find a better line of work. They pile their belongings into their truck and tell a neighbor named Nancy that they are moving to Bixbee, and despite Nancy’s offer of a job with free lunch and beer thrown in, the fellows turn her down. Leaving Perfection, they brag that nothing stands between them and Bixbee. However, they stop when they see Edgar Deems sitting high on an electric tower. Valentine climbs up and finds him dead. Jim, the local doctor, tells them Edgar died of dehydration. Valentine and Earl cannot figure out why he died of thirst on the tower, unless something waited for him below. Meanwhile, “Old Fred,” a farmer, notices his sheep are restless. Something grabs him from below. Nearby, Rhonda picks up vibrations on her seismograph. As Valentine and Earl drive past Fred’s farm, they see the fence knocked down, the sheep slaughtered, and they find Fred dead, buried up to his neck. They warn road workers Howard and Carmine that a killer is on the loose, but the two workers carry on. However, as Carmine jack hammers the edge of the pavement, he hits something that bleeds. His jackhammer pulls away, and the pneumatic line wraps around his leg and carries him away. Howard tries to rescue his co-worker, but falling boulders crush him. Valentine and Earl return to Walter Chang’s Market to make a telephone call and find the line dead. They warn Chang and his customers--Miguel, Melvin Plug, and Nestor--about Old Fred, and Nestor asks them to drive to Bixbee to get police. However, rocks block the road at the worksite, and they find Howard’s hardhat filled with chunks of brain matter. Leaping back into their truck, Valentine has a hard time pulling forward because something has grabbed the axel. He finally breaks free, and they return to Perfection. When they arrive, everyone is shocked to see a bloody tentacle wrapped around the axel, ripped from whatever it was attached to. Burt Gummer uses a shovel to get it off, thinking it is some kind of snake. He reckons that if Old Fred and his sheep were all killed, there must be more creatures out there. Meanwhile, as Dr. Jim and his wife, Megan, look for their generator, they discover that it has been pulled underground. Dr. Jim yanks on the cord, and something pulls him underground. Megan runs to their station wagon, and snakelike creatures give chase and bang on the car windows. The ground collapses beneath her and swallows the vehicle. At a group meeting at the market, Burt Gummer discusses setting perimeters and standing guard. Walter informs everyone that his citizens band (CB) radio cannot reach outside Perfection Valley because of the surrounding mountains. Miguel suggests saddling Walter’s horses and riding the thirty-five miles to Bixbee, and everyone decides that Valentine and Earl are the best riders. Valentine gets a pistol, and Heather Gummer gives Earl her high-powered rifle. Valentine and Earl find Dr. Jim’s trailer empty and the station wagon gone, but hear its radio underground. As they proceed toward Bixbee, their horses shy and throw them off. The ground opens up and a giant wormlike creature emerges and grabs one of the horses. Valentine and Earl run to a concrete barrier. The creature, traveling underground, cracks through, but is killed by the impact. Rhonda LeBeck appears moments later and asks if they have seen anything “weird.” Valentine and Earl enlist her to help to open the shattered concrete wall and pull out the large dead creature. Noting that it has no eyes, Rhonda surmises that it is subterranean. Its tentacles appear to shoot out of its mouth. She declares it “the biggest zoological discovery of the century.” Looking at her various seismographic readings, Rhonda guesses there are at least three other wormlike creatures in the area. They walk to one of her seismographs, but when the needle jerks back and forth, they run to a rock formation for protection and arrive just as tentacles reach out to grab them. Though safe, they are trapped, and Rhonda's truck is far away. When Valentine taps the ground with a board, a huge worm emerges and grabs it. Rhonda guesses the creature feels their vibrations through the rocks. The next morning, Valentine tosses a shovel and the creature grabs it. Finding poles, they pole-vault from rock to rock until they cross the desert floor to Rhonda’s truck. Returning to Perfection, they find that Walter Chang cannot contact Burt and Heather on his CB. Marking all known sightings on a map, Valentine realizes the worms are making their way to Perfection. Rhonda suggests they all move west toward the mountains because of the granite terrain. Suddenly, a worm attacks Melvin Plug outside, but he escapes into a shed. Nancy and Mindy run into their house for protection, and Valentine jumps into the back of a pickup truck. As two creatures attack from the different direction, Rhonda gets caught in barbed wire and Valentine rescues her by attacking the worm with a pick. Inside the market, a worm emerges through the floor, grabs Walter Chang, and drags him under. As another creature comes through the floorboards, everyone climbs the shelves to the roof, except Rhonda, who is thrown through a window when a tentacle knocks over the shelves. She climbs to safety on the town water tower. The others call out to Melvin, Nancy, and Mindy to climb onto their roofs. Elsewhere, Burt and Heather radio the market from their compound. Valentine retrieves Walter’s CB and explains what is happening. As Valentine sees a worm burrowing at top speed toward Burt’s bunker, he warns him and Heather to get on the roof. The bunker’s cinderblock walls collapse and the couple open fire, blasting the creature until they kill it. Valentine reminds them on the radio that there are still two more. From their perch atop the market, Valentine and Earl see a creature shaking the foundations of Nancy’s house. Since Nancy and Mindy have been sitting quietly on the roof, they are not sending vibrations, so Valentine guesses that the creature is trying to “figure out” the house. When a creature knocks over Nestor’s trailer, he flies off the roof and is sucked underground Valentine radios Burt and Heather to alert them the creatures are tearing down the town from below, so they will need leave. When a worm destroys the last working truck, Earl wonders if they can escape on the town bulldozer. As the roof of the market buckles, Valentine and Earl lower Miguel to a lawn tractor, which he turns on and sets into motion. Driverless, it lures the two creatures away from the buildings. Valentine leaps off the roof and runs to the bulldozer, but when the lawn tractor turns over, the creatures stop, turn around, and chase Valentine. He stops dead in his tracks, hoping the creatures will not find him. The other humans make noise, and Rhonda distracts the worms by knocking over a water pipe on the tower. Valentine hooks the bulldozer to an old trailer and rides around the town, as the others jump on. The Gummers join with their best guns and a bag of homemade bombs. They ride toward rocky terrain, but suddenly the road collapses and pitches them off the bulldozer. The shock of one of Burt’s exploding bombs sends the worms running, but they hurry back. The humans run for the rocks, tossing more bombs to scare off the worms, but once they reach safety, they are again trapped. As they toss stones to attract one of the worms, Earl lights and tosses one of Burt’s bombs. The worm grabs it and is blown up in the explosion. They try the same tactic on the other creature, but it spits the explosive back at them and blows up Burt’s satchel of bombs, scattering Valentine, Earl, and Rhonda. Armed with the only remaining bomb, Valentine starts running, with Earl and Rhonda right behind, and the giant worm hot on their trail. Valentine lights and tosses the bomb, but it lands behind the creature. However, the explosion drives the worm forward and sends it over a cliff. The creature smashes to pieces on the rocks below. Later, Valentine and Earl prepare to leave town, but since Rhonda has decided to remain in Perfection to cover the story for science magazines, Valentine decides to stay with her. They kiss to seal their relationship.