The movie opens with a young couple, Pat Wheeler (Grady Vaughn) and Liz Humphries (Yolanda Salas), parked in a bleak, rural locale overlooking a ravine. A giant Gila monster attacks the car, sending it into the ravine and killing the couple. Later, some friends of the couple decide to assist the local sheriff (Fred Graham (actor)) in his search for the missing teens. Chase Winstead (Sullivan), a young mechanic and hot rod racer, locates the crashed car in the ravine and finds evidence of the giant lizard. However, it is only when the hungry reptile attacks a train (a model train set substituted as a low-budget effect) that the authorities realize they are dealing with a (roughly) 70-foot long venomous lizard. By this time, emboldened by its attacks and hungry for prey, the creature attacks the town. It heads for the local dance hall, where the town's teenagers are gathered for a sock hop. However, Chase packs his prized hot rod with nitroglycerin and rigs it to speed straight into the Gila monster, terminating the lizard in a fiery explosion and heroically saving the town.