In Oregon, a meteor crashes into Crater Lake and heats the water, hatching a dinosaur egg. Months later, fishes have vanished from the lake and a huge dinosaur hunts cattle and human to feed. The local Sheriff Steve Hanson investigates the mysterious disappearance of tourists and even a criminal. He also tells to the rednecks Arnie Chabot and Mitch Kowalski that they shall not rent their boats to the tourists. When he discovers the dinosaur, his friend Richard 'Doc' Calkins and two scientists asks him to leave the animal alive for the scientific community. Will Steve let the dinosaur live?