Melvin White, a neurotic, accident-prone cop who gets demoted to the night shift, secretly moonlights as the Unknown Comic, an anonymous stand-up comedian who performs with a paper bag over his head. When someone using the same guise commits a string of bar robberies in town, some begin to suspect that White is the culprit.

Toxic waste dumping in a small Idaho town turns a young boy into horrible mutant monster. The town's police chief and a government scientist team up to stop the monster, which is quickly killing off the town's citizenry.