Pine Cove suffers a major crisis when the town psychiatrist, Val Riordan— who has been haphazardly issuing prescriptions instead of dealing with the real mental problems of her patients — suffers a sudden bout of guilt and substitutes all of her patients' anti-depressants with placebos. At this same time, by coincidence, human-generated environmental activity stirsa prehistoric sea-beast from its underwater keep to come ashore.
In addition to its ability to change form, the beast exudes a pheromone that inspires uncontrollable lust among the residents of Pine Cove and also lures some of them as prey. After mistakenly trying to mate with a fuel truck (causing an explosion), the beast hides in a trailer park, attracting the curiosity of local crazy lady and former B-movie star Molly Michon, who builds a rapport with the injured beast.
Meanwhile, Theophilus Crowe, the town constable, investigates a strange suicide, the activities of his corrupt boss, and his adversely affected marijuana habit. When the beast (whom Molly has named "Steve") starts eating residents of Pine Cove and interfering with Theo's boss's methamphetamine business, Molly (who has become romantically involved with the beast) and Theo band together to make possible the beast's safe escape and to take down the boss at the same time.