While Earl and Val became wealthy with their discovery of the Graboids, Earl lost most of his fortune through an ostrich farm and other investments. Earl is approached by two men, Grady Hoover and Señor Ortega. Ortega knows that Earl and Val dealt with the Graboids previously. He informs Earl that there are more of them killing workers at the Petromaya Oil Field; he needs help to dispose of them. Earl refuses, horrified at the prospect that there are more of the creatures that almost killed him. Grady tells him that Ortega will pay him $50,000 for each graboid. Earl agrees to eliminate the Graboids, and Grady accompanies him.On their way to the Petromaya Oil Field, Earl and Grady are introduced to Pedro, the company's chief engineer and Kate Reilly, a geologist. Ortega brings Earl and Grady a few cases of dynamite and an CAR-15. A man named Julio introduces a seismic monitor that will show Grady and Earl where the Graboids are. Grady builds a chain with a few empty aluminum cans attached to it to attract the Graboids.Earl and Grady kill 16 Graboids using dynamite strapped to remote-control toy cars. Another Graboid snags the chain Grady hooked to the back of the truck. The Graboid begins dragging them across the field. When the Graboid snaps the chain Earl sees more Graboids approaching on the seismic monitor. Earl calls up Burt Gummer, an old friend of his who helped him take down the Graboids with Val. Burt comes in with an army truck filled with explosives and weapons. The group splits up to kill more of the Graboids.Earl and Grady see another Graboid on the seismograph. Oddly, the Graboid is moving away from them, so Earl and Grady investigate. Upon reaching the top of a hill, the Graboid surfaces. In a panic Earl backs his truck down the side of the hill and into a pile of rocks, breaking an axle. They see the Graboid has not moved. Earl and Grady wait for Pedro to bring the Graboid back to the refinery. The Graboid makes loud, painful noises, and Grady and Earl see some of the insides of the Graboid are missing, leading Earl to believe that something emerged from it.While Earl tries contacting Kate over the radio, he notices that the radio's transmitter has been damaged, then he and Grady hear another Graboid making a noise just like that of the one they encountered earlier. Grady sees Pedro's truck coming up the road only to stop. When Earl and Grady walk to the truck, they see it is damaged and all that is left of Pedro are his severed arms. Earl decides to call for help by hiking to a nearby radio tower.Burt has become worried that his monitor is showing no Graboids and begins returning to the refinery. When Grady and Earl reach the radio tower they find it has been damaged. Earl spots a car near a small bar that Grady tries hotwiring. The two hear a strange noise coming from the bar, then see a creature resembling a smaller two-legged Graboid, dubbed a "Shrieker", emerge from the bar. Grady and Earl kill it, but three more Shriekers come for them. They drive the car back to the refinery. As Burt is trying to get back he is ambushed by Shriekers.Kate, unable to contact anyone, grows worried. Julio agrees to find them. As he is about to leave a Shrieker devours him. Grady and Earl kill the Shrieker that killed Julio and reunite with Kate. As they are about to leave another Shrieker appears and begins damaging their car's engine, but Earl kills it. Burt arrives with his truck damaged from the Shriekers that attacked him. He shows them a Shrieker he caught alive, unaware that another Shrieker has stowed away underneath his truck.The four discover that the Shrieker hunts by using a heat sensor on top of its head, explaining why the Shriekers attacked the cars and the radio tower. When it consumes a piece of food it creates another Shrieker. While enjoying this spectacle, Kate, Earl, Grady and Burt are ambushed by Shriekers. The group plans to drive off with Julio's car, but another Shrieker is blocking their path. Burt uses his .50 BMG rifle to kill it, but the bullet goes through the Shrieker and damages the engine block of Julio's car. More Shriekers trap Grady, Earl and Kate on top of an oil tower and Burt in the bucket of a tractor.The Shriekers start jumping onto each other's backs to reach Grady, Earl and Kate. Burt makes the Shriekers chase him into the storage compartment where his truck is. He is able to lock a door and close a garage, trapping them. However, this proves to be problematic as the garage is filled with food and allows the Shrikers to reproduce at a rapid rate. Earl sprays himself with a fire extinguisher to make him cold so that the Shriekers will not see him, so that he can reach Burt's bombs.As he is walking the frost from his body dissolves and the Shriekers see Earl in Burt's truck. Earl sets off a timed charge and throws it in the back of Burt's truck. Grady, Burt and Kate pull him out with a hose, and the four run from the refinery. The bomb detonates the explosives in Burt's truck and destroys the refinery, killing the Shriekers.Grady tells Earl that the Petromaya corporation owes them for 28 worms they killed. As they walk towards the remains of the refinery, Earl suggests they charge the corporation for the Shriekers they killed. When Grady says that they can open up their own Monster World, Earl says, "No way.", but Grady says, "Oh, C'mon, Earl. This could be like your big third chance".
Output: Question: What allows the Shriekers to see heat?, Answer: Through special infrared receptors