After spending all the reward money from his first encounter with the giant man-eating worms called Graboids, Earl Bassett (Fred Ward) agrees to hunt more of the deadly creatures at a Mexican oil refinery for $50,000 each. Knowing that he cannot face the monsters alone, Earl recruits Burt Gummer (Michael Gross), another veteran of the incident in Nevada, to supply the firepower. There is only one problem: The Graboids have now evolved to attack above ground.