Giant worms descend on the small town of Perfection, Nevada.
Old Fred sees Edgar walking his donkey and pulls over and gives Edgar a bag full of carrots from his farm. They make a plan to play cards on Thursday and Edgar promises to bring the liquor. As Edgar puts his donkey in the barn he hears a noise and Justine, his donkey, disappears. He grabs his rifle and is chased by something underground. Valentine McKee pees over the edge of a plateau while Earl Bass sleeps in the bed of their truck. Valentine spots some cows nearby and plays a prank on Earl by yelling stampede and shaking the truck. They trade each other a cigarette for a lighter and then play rock, paper, scissors to see who has to make breakfast. As they are nailing barbed wire to a fence, Earl talks about quitting their lives as handymen and finding other work. As they are driving towards town Valentine sees the new seismology graduate student's truck and veers off the road to meet her. He stops and Rhonda LeBeck greets them and asks them if they know if anyone has been drilling or blasting in the area and they tell her no. She tells them her seismographs have been picking up weird readings and they tell her they will ask around when they get into town. Earl tells Valentine, maybe they should check on the seismographs for Rhonda and then chastises Valentine for not approaching women that don't match exactly what he is looking for.
They drive into Perfection and stop at Walter Chang's Market. Earl warns Melvin Plug not to mess with their truck as he and Valentine walk into Walter's Market. Inside, Burt Gummer is arguing with Walter about the ammo he special ordered for him and Heather Gummer. Earl and Valentine grab a beer and tell Walter, Burt and Heather about the seismographs and Burt warns if Rhonda finds something then the Federal Government will come in and take over their land. As Rhonda is packing up for the day, a Graboid follows her and nearly gets her before she gets into her truck and drives away, oblivious to the Graboid. Valentine and Earl drop off Nestor's trash to the dump and Valentine tells Earl they need to set their sights higher. While they are pumping Melvin's septic system, raw sewage starts shooting out all over them from a loose hose. They go back to their trailer and shower and pack up their belongings in their truck and drive away. Nancy flags them down and Earl asks Mindy how many hops she has continuously hopped on her pogo stick. Nancy offers to give them a months work in order to build her a kiln, but they continue on their way to Bixby. They see Edgar high up on a transmission tower. They stop and Valentine climbs up the tower to get Edgar down. He finds Edgar dead and Valentine and Earl put Edgar's body in their truck and bring it to Jim - The Doctor who tells them Edgar died of dehydration. Old Fred is tending his crops when his sheep start to spook. He is then suddenly pulled into the ground. Rhonda notices large spikes in her seismograph and checks to see if her equipment is damaged.
Valentine and Earl speed past Howard - Roadworker and Carmine - Roadworker, but stop when they see Old Fred's sheep torn to bits. As they are looking for Old Fred, they find his head buried in the dirt. They drive back the way they came and tell Howard and Carmine there is a killer on the loose. Carmine doesn't believe them, but Howard grabs a crowbar. As Carmine is breaking up the road with a jackhammer, it impales into a Graboid which screams and quickly moves away, dragging Carmine with it and eventually pulling him underground. Howard goes to help Carmine and is killed by a rock slide. Miguel tells Walter that some of his cattle are missing. Valentine and Earl walk into Walter's store while telling Melvin and Nestor about Edgar and Old Fred. Valentine tries to use Walter's phone, but the line is dead. Nestor tells Valentine that they have to go to Bixby to bring the police. Valentine and Earl drive back the way they came, but are forced to stop due to the rock slide. They get out of their truck and find a hard hat with brain matter inside. As they are trying to drive away, the truck gets stuck on something. Mindy sees Valentine and Earl drive back into town and they park their truck in front of Walter's store. Mindy sees something latched onto Valentine and Earl's truck, and Burt uses a shovel to detach it and Walter haggles with Valentine and Earl for it. Burt tells the others he thinks there must be more somewhere.
As Jim and Megan - The Doctor's Wife are finishing up working on their house for the night, their generator disappears. Jim starts to pull on the chord stuck in the ground and is then grabbed and killed by a Graboid. Megan runs to their car and the car is pulled underground along with Megan. The residents of Perfection have a meeting and Burt suggests they arm themselves and Miguel comes up with the idea for two people to take Walter's horses and ride to Bixby. Earl and Valentine are picked to go and as they are riding towards Bixby they stop by Jim and Megan's property and find the car buried in the ground. They ride away and the horses start to get spooked and buck them off. A Graboid pops out of the ground and starts to chase Earl and Valentine. They jump across a cement canal and the Graboid kills itself by ramming into the concrete. Rhonda walks up to them and asks them if they noticed anything weird a moment ago and sees the dead Graboid. They pry the Graboid into the canal and Rhonda has a theory on how it moves and tells them there are probably three more Graboids. As they are walking towards Rhonda's truck, they are chased by another Graboid and climb onto a large boulder. They try and wait out the Graboid, but it is waiting for them when they check to see if it is still there. Rhonda realizes the Graboids can sense seismic vibrations and they end up sleeping on the boulder overnight. Rhonda comes up with the idea to use a long stick to pole vault to her truck after they find the Graboid still waiting for them. They get into Rhonda's truck and drive back into town and tell the others about the Graboids.
Valentine thinks they should leave, but most of the others think someone will come when they discover the phone lines are down. Outside of town, a Nev-Cal Tel truck sits abandoned near the buried body of two phone company workers. Valentine pulls off a map of Perfection Valley from the wall and points out that the Graboids are heading in the direction of the town. As they are talking, Walter comes up with the name Graboids. After playing a prank on Earl, Melvin screams and they find him up a light pole. A Graboid emerges from the ground and everyone runs into Walter's store except Nestor and Melvin. They hear Mindy jumping on her pogo stick and Valentine grabs her shortly before Nancy runs to her. A Graboid grabs the pogo stick and Nancy and Mindy runs into their house while Valentine jumps onto a truck. Another Graboid comes and Rhonda gets stuck in barbed wire while she is trying to run away. The Graboid starts to pull Rhonda towards it and Valentine helps her. They run back to the store and the drink refrigerator turns on and starts to make a loud noise. A Graboid bursts into the store and drags Walter underground. The other Graboid breaks into the store and Earl, Valentine and Miguel climb to the roof while Rhonda climbs up a water tower. Valentine tells everyone to get onto their roofs. Burt and Heather come home from hunting for the Graboids and Heather sees everyone on their roofs. Burt calls Walter on the CB and Valentine tells him the Graboids are heading in his direction and to get on their roof.
Heather and Burt arm themselves and a Graboid bursts its way into their basement. They manage to kill it with an elephant rifle and tell the others they killed it, and Valentine tells them there are still two more. The Graboid that originally attacked Valentine and Earl's truck starts to attack different buildings to test their structural integrity. It pushes over Nestor's trailer and pulls him underground. Valentine calls Heather on the radio and tells her they have to leave together and before she and Burt can drive their truck to pick up the rest, a Graboid grabs it and destroys it. Earl has the idea to use the bulldozer to pull a trailer to carry everyone to safety. Miguel has the idea to use Walter's riding lawn mower to distract the Graboids while Valentine runs to the bulldozer. The lawn mower hits a berm and turns over and the Graboids race towards Valentine. Rhonda yells to Valentine to stop and breaks a pipe leading to the water tower, which attracts the Graboids. Valentine runs to the bulldozer and attaches the trailer to it and picks up the others.
Burt and Heather make pipe bombs and get into the trailer with the others. They drive towards the mountains, but before they can reach them, the Graboids set a trap and dig a pit in the direction the bulldozer is heading, causing it to crash. Burt uses a pipe bomb to make the Graboids run away, but they come back again. They use another one to make them run away while they run towards a set of boulders. Burt tells Heather that if it comes to dying by the Graboids or starvation, he plans on letting them take him while he is holding a lit pipe bomb. Earl has the idea of attracting the Graboids and then feeding them a pipe bomb. They manage to kill one, but as they try it against the last one, it spits the pipe bomb back at them. Valentine, Earl and Rhonda are forced to run off the boulder and as they try to run back, the Graboid emerges in front of them. Valentine has the idea to use himself as bait and runs towards the edge of a mesa. Earl runs after him followed by Rhonda who hands Valentine a lighter to light the fuse on the last bomb. Valentine uses the bomb to make the Graboid run towards the edge of the mesa and it falls to its death. Back in town, Rhonda takes a photo of Valentine and Earl and then comes and talks to Valentine. She says bye to him and Earl and Earl nudges Valentine to ask her out. Valentine walks up to Rhonda and kisses her.