Prominent movie actress Monica Madison exits a cab in front of the Can Can Club late one night. Instead of going inside, she crosses the street, where she is strangled to death by an unseen assailant, who rips the diamond brooch from the choker around her neck. Later at the crime scene, Capt. Kroger reprimands detective Stevens because he is drunk, even though he is off-duty. Stevens, who had been drinking at the club and does not remember what he has been doing the past few hours, learns from the club’s janitor, George, that he left the club hours earlier with a blonde woman. Meanwhile, Alex Voe, an artist whose wife Peggy works as a waitress at the Can Can Club, is one of many bystanders at the crime scene, but goes home when he learns that his wife left work early. Alex arrives just as Peggy reaches her door and is confronted by Claude Almstead, Monica's mentor, who had been following Peggy. Although it is two o’clock in the morning, Claude wants to hire Alex to draw his caricature. When Alex and Peggy are alone in the kitchen, they fight about money and Alex’s depression and drinking, until Peggy throws him out. While the couple argue, Claude surreptitiously steals one of Alex's sketches, then consoles Peggy by offering to take her for a drive. In the meantime, Stevens hopes to repair his reputation with his captain by conducting his own investigation while off-duty, and learns from Sgt. Duane, who is leading the official investigation, that Monica scratched her killer. Moments later, Peggy’s co-worker Connie bumps Stevens’ arm, which begins to bleed, but he hides the blood, and George mops up the floor to protect him. While Claude takes Peggy to his expensive, modern home, Stevens goes to Connie's apartment to question her further, and learns that he left the club that night with a woman named Candy Price, who lives in the same building as Peggy. Stevens goes to see Candy, a blonde seductress who has been waiting for him for four hours. While he is there, the radio re-broadcasts an interview with Monica and Claude that was made earlier in the evening at her movie’s premiere. Stevens arranges to meet Claude at the club, where Duane protests Stevens’ involvement in the investigation, but when Stevens confesses he is only trying to make things right, Duane relents. Stevens then talks to the radio announcer, Larry Jackson, who says that Monica and Claude were having a disagreement during the premiere. Upon returning home, Alex discovers his wife is gone. While leafing through the sketchbook, he finds a drawing of Claude and remembers sketching him on the same night he drew Monica. After showing the sketch to the policemen, Alex reveals that he saw Claude watching Monica at the club a couple of weeks before, and that he is now worried because he believes Peggy is alone with Claude. When Alex leaves the club, he is met by Candy, with whom he is having an affair. Alex tells her that he has renewed love for his wife and wants to end their relationship, just as Claude arrives with Peggy in the car. Alex accuses Peggy of having an affair and she runs home, after which Alex follows Claude into the club. There the police question Claude, and although he initially refuses to speak without a lawyer present, he relents and admits that he loved Monica but did not kill her. When Duane threatens to rough up Claude, Stevens strikes the officer, who hits him back, and Claude escapes during the ensuing fistfight. Alex, meanwhile, calls Peggy to apologize and warn her that Claude is a murderer, but is too late because Claude is already inside their apartment. Terrified, Peggy runs outside and encounters Alex, who is enraged and incoherent. When Candy approaches them, Peggy runs away, and Alex angrily grabs Candy and demands she obtain the caricature that Claude stole from him. Candy promises to help, and Alex confesses that he blackmailed Monica to get money for Candy, then killed Monica when she threatened to go to the police. When Candy cries for help, Alex strangles her to death, and is shot by Duane after he tries to flee. Afterward at the club, Claude explains that he had originally approached Peggy to tell her about Alex’s affair with Monica, which began when he worked as an artist on her film. After Alex tried to blackmail Monica about their affair, she threatened to go to the police and ended their relationship. Claude became jealous when she then announced she was marrying a producer, and they argued about it at the premiere, after which she ran out. By the time Claude arrived at the club, she had already been murdered, and the diamond brooch he had given her was missing. Later at Alex's apartment, Claude discovered a caricature of Monica in Alex’s sketchbook, which showed her wearing the brooch, and discovers the brooch itself in Alex’s portfolio. With the murder mystery solved, Duane takes Claude and the distraught Peggy to police headquarters to make statements. Stevens, who had feared he may have committed the murder during his “lost” hours, still does not remember what he did during that time. Joe, the club's owner, and George finally are able to close the nightclub.