Researchers from the local university make an astounding discovery in an ancient cave near Crater Lake. Breaking into an unkown tunnel, they find prehistoric paintings on the walls that depict humans battling a gigantic dinosaur. But weren´t dinosaurs extinct by the time man arrived on the scene? The answer isn´t long in coming. A meteor has crashed into the lake, incubating an egg that lay dormant for ages. A monstrous aquatic dinosaur emerges from the depths, wreaking havoc on the once-peaceful town. The researches, Dan, Susan, and Doc, come up with a daring plan to capture the beast alive, for the sake of science, but they´ll have to race against time and a dedicated sheriff, Stee Hanson, who´s ready to blow the creature back to kingdom come.