Melvin White is an inept police officer who finds himself demoted to night patrol by a pathologically deceitful captain whose own quirks (including a running habit of flatulence) complicate every shift. His partner, Kent Lane, is a veteran of ten years who seems to care little for crime-fighting and more for chasing romantic escapades in the back of their patrol car. Another colleague, Sue Perman, is drawn to White's company, though he consistently reads her hints as friendship rather than romance.
During the course of a single, eventful night, White and Lane stumble into a string of odd assignments that blur the line between duty and farce. They encounter a couple parked in front of a fire hydrant, join a group of colleagues in a marijuana smoke break, and even encounter a male rape victim whose high-pitched voice adds an unusual note of tension to the night's work. By day, White’s life is chaotic, but by night he steps into the world of entertainment as The Unknown Comic, a stand-up persona that wears a paper bag over his head with eye and mouth holes.
This alter ego propels White into the spotlight and attracts the attention of a talent agent who believes the masked comic could become both famous and rich. Meanwhile, Edith Hutton, a devoted fan of White and his stage persona, becomes obsessed with discovering who lies behind the bag and would even leave her own boyfriend to meet the man beneath the disguise. White himself alternates between his police duties, his onstage persona, and regular sessions with a psychiatrist, underscoring the film’s mix of danger, humor, and psychological strain.
Things take a darker turn when a thief begins robbing bars while dressed as The Unknown Comic. Although no one knows the thief’s true identity, White’s captain grows increasingly suspicious that White himself might be involved. To clear his name without exposing his secret identity, White teams with Lane to hunt down the impersonator. He is scheduled to perform at a venue as The Unknown Comic, but his undercover pursuit of the thief prevents him from taking the stage.
The tension escalates as impersonators clash with the real performance. One impersonator appears on stage to perform, while another breaks in to steal money. White and Lane give chase, leading to a climactic, Western-style gun duel where White emerges victorious. The first impersonator is revealed to be White’s own psychiatrist, who coveted a quick fortune by exploiting the performer's identity. White then tracks down the second imposter, who turns out to be Perman. She had used a recording of White’s voice to shield him from arrest. The film culminates with Perman and White sharing a sexually charged moment at White’s apartment, closing a night that blends crime, comedy, and celebrity obsession into a single, unruly arc.
