 When an army of Graboids -- giant, carnivorous underground worms -- threaten the Petromaya oil refinery in Mexico, its owners call on Earl Bassett, who once helped kill four of the creatures in Perfection, Nevada. Having squandered the money that came from his resulting celebrity status, Earl is convinced by the $50,000-a-head bounty offered, as well as the enthusiasm of admirer Grady Hoover, who becomes his partner. At Petromaya, Earl and Grady meet geologist Kate Reilly, and begin Graboid hunting, tricking several Graboids into swallowing bomb-rigged, remote-controlled cars. When they find they re facing a lot more Graboids than they ever expected, Earl calls his friend Burt Gummer, a survivalist who arrives well-stocked with weapons. It s not long before Earl and Grady discover a dead, hollowed-out graboid and find that it has birthed human-sized, two-legged offspring that chase their prey on land, and find their prey by sensing heat, such as the heat given off by a person s body temperature. These creatures come to be known as Shriekers. A swarm of Shriekers soon has Earl, Grady, Burt, and Kate trapped in the refinery, and the Shriekers are stopping all of their efforts to escape. All of the usual methods of getting rid of Graboids won t work on Shriekers, so Earl, Grady, Burt, and Kate are going to have to come up with something new to fight the Shriekers with.