Natives of a small isolated town defend themselves against strange underground creatures which are killing them one by one.
A small town gradually becomes aware of a strange creature which picks off people one by one. But what is this creature, and where is it? At the same time, a seismologist is working in the area, she detects _tremors_. The creature lives underground, and can 'pop up' without warning. Trapped in their town, the town-folk have no escape.
A group of people in a small peaceful town named "Perfection" located in Nevada. The peace becomes hysteria once people are being killed underground in mysterious ways. The town then investigates, and will do anything to protect their town and their selves.
Trying to escape their dead-end life in the desert town of Perfection, Nevada, Valentine "Val" McKee and Earl Bassett find themselves sidetracked when corpses mysteriously start piling up around them. When Val and Earl have a run-in with some creepy tentacled creatures that have made lunch out of a road crew, they retreat back to the town to spread the news. Although these monsters are not exactly intellectuals, their mental powers are still mind-boggling. Detecting a human hiding in a car, they dig under the vehicle, causing it to sink into the earth. Val and Earl get help from several townspeople. With the help of Rhonda, Val and Earl kill one of the monsters. But there are three of them left, and they are each about 30 feet long. Walter starts calling the monsters graboids. When the survivors think they have outwitted the graboids by taking refuge atop the roofs of buildings, the graboids merely destroy the buildings' foundations, killing two people. The graboids are quick learners when it comes to stalking their prey, and the humans must continually be on their toes if they are to stay alive while they try to find a way to defeat the graboids.
- Valentine "Val" McKee (Kevin Bacon) and Earl Bassett (Fred Ward) are two good-for-nothing odd-job workers. They usually mend fences and railings, help farmers in a sleepy town called Perfection, and take care of cows. They have the use of a down-trodden truck, and not much money to their names. The live near a dry dusty town, and are friends with most of the villagers. Perfection occupies a small part of dried-out Perfection Valley, surrounded by small mountains, except for a county road.
Rhonda LeBeck (Finn Carter), is a university student which investigates earthquakes. She tells them that she's getting weird signs from their seismographs, but there were no earthquakes around. Val likes her, but prefers daydreaming about some playmate, so he doesn't ask the seismologist out.
One day Val and Earl they find the town drunkard, Edgar, on the top of a electricity tower, dead, with a rifle in his hands. They start wondering whether he was so afraid of something that he preferred dying up there of thirst. They take him to the doctor who confirms that Edgar died of dehydration but leaves his death unsolved. Miguel, a local cattle rancher, also talks about how a good number of his herd disappeared without a trace.
One night at the doctor's trailer, where he and his wife live while building a house, the doc hears a strange noise and sees a natural phenomenon like a steam vent spewing from the ground. He goes to investigate, thinking they may have discovered a natural gas pocket. Suddenly, the ground beneath him collapses and he's pulled forcibly down into the hole, screaming in pain while his wife tries to pull him out. She frantically digs in the ground and a snakey head pops up and hisses at her. She retreats to their car but whatever attacked her husband begins to pull the car under the surface.
Disenchanted with the odd jobs they perform for the townsfolk, Val and Earl decide to collect their meager possessions and head out of town, even turning down a lucrative job from the local potter, Meghan, to build her a new ceramic oven, where she also offered them all the free beer they wanted. Heading out of town, they stop by Old Fred's farm and find he's been decapitated, his head lying half-buried under his Fedora. Thinking there may be a murderer on the loose. They also discover the doc's car when they hear the stereo still on and the headlights sticking up vertically. On the road they find it blocked by a small landslide. Assuming it was caused by the two road workers, they get out of their truck to yell at them and find the men's helmets lying in the road full of blood and slime. When they try to leave, Val back into a small ridge and gets stuck. They eventually shake the truck loose and head back into town. When they get there, they discover a long, snake-like appendage wound around the rear axle.
The shopkeeper, mean Walter Chang (Victor Wong), lends them two horses so they can go and tell the county police, because all phone lines are cut, and there is no mobile phone network coverage on the area. Several people are not worried at all in spite of everything that's going on: dumb teenager Melvin Plug (Robert Jayne) mocks them, Burt and Heather Gummer (Michael Gross and Reba McEntire) have built themselves a nuclear refuge and crammed it with heavy weaponry, so they don't feel they need to have fear of anything.
Val and Earl ride as fast as they can but their horses are suddenly spooked by some of the snakes. They run away on foot, but the creature runs after them. As they run, they try to jump across a concrete ditch; the creature chasing them suddenly hits the wall of the ditch, killing itself. At that moment, the seismologist shows up again. They discover that the creature stinks horribly, is several metres long, and that the snakes were a kind of tentacles protruding from its beaked mouth. Rhonda checks her seismographs, learning that there must be at least three more of those snake-mouthed monsters.
When the three are going back to Perfection another of the creatures tries to capture them. They can only see a trail of dust flying as the monster swims invisible through the soft soil of the valley. This dust trail is going to be the sign that a critter is moving underground from now on. Val, Earl and Rhonda run for dear life and end up up to some tall rocks where the creatures cannot climb. They stay there, but the creatures are very patient. Finally, Rhonda devises a plan hey manage to climb from one rock to the other and to jump into their van, being closely followed by the hungry monsters. They deduce that creatures feel them because they can make sense of the noise humans make in the form of vibrations, either by simple movement or talking.
Back to the drugstore, Walter decides to call the monsters graboids. Melvin is still mocking Earl and Val stupidly, but Val has to risk her life to save Mindy Sterngood (Ariana Richards), who had been hopping around with her headphones on, not listening to her mother Nancy (Charlotte Stewart)'s cries. When they think they have outwitted the graboids by taking refuge atop the roofs of buildings, the graboids destroy the buildings' foundations. The buildings are simple and fragile, completely made of planks of wood. A graboid manages to eat Walter, emerging from under the cheap wooden shopfloor. Another graboid eats Nestor (Richard Marcus), and one of them manages to destroy one of the underground walls of the Gummers, but they fight back with all their weaponry, finally killing the vicious creature.
The survivors pick up a bulldozer and they try to run on it. They also go to pick up the Gummers, which have prepared many weapons. The graboids are highly intelligent, and they prepare a trap for the humans, which succeeds. They all have to run to some rocks. They wait there, surrounded by the graboids.
They think of another plan. They throw dynamite to the animals, who swallow everything but are afraid of strong noises, which hurt their sensitive sense. The dynamite explodes within one of the critters, killing it. They try the same trick with the other graboid, but the remaining critter spits out the dynamite, and they have to run away from their safe hiding place. Val is on the open earth, so he is going to be detected and eaten by the surviving graboid. He decides to run, but the graboid is very fast. When Val is about to jump from a high cliff, he steps aside, but the graboid can't stop because of the distraction of their last dynamite blast, and falls from the cliff onto the void.
They are happily alive, and Earl coaxes Val into asking Rhonda out. Val tries to fight it, because Rhonda is a university student with a brilliant future in front of her, and he has no prospects. Earl tells him that it's her who has to take a decision like that.
The final scene shows some loose dirt moving on the dry soil of the valley, proving that there is at least one more ravenous creature alive.