After his son, private detective Eddie Delaney, tells him that he is joining the army soon, police sergeant Timothy J. Delaney continues his rounds and investigates suspicious movements at a warehouse. He questions former bootlegger Marty Clark, who claims that his presence there is legitimate. Actually, Clark has arranged for the hijacking of two trucks, which contain tires he intends to sell on the black market, and shoots Tim as he is about to discover the stolen goods. Before dying, Tim manages to shoot two holes in Clark's escaping car. Meanwhile, the owner of the trucks, John Underwood, anxiously awaits their arrival, for even though he owns the tires, it is illegal to transport them due to wartime regulations. When his drivers show up wounded, Underwood realizes what has happened and complains to his secret partner, to whom he has been paying protection. Soon after, Eddie confers with police detective lieutenant William Decker, who urges him to work with the police solving Tim's murder. While Decker is questioning Clark about the wounded drivers, Underwood hires Eddie to find out who hijacked his trucks. Eddie goes to the hospital where Underwood took the drivers, but they are murdered before he can speak to them. Outside the hospital, Eddie sees the car that was shot by his father, and then sees it again by Clark's nightclub, where he has gone to meet Decker to discuss the case. Decker leaves to get a warrant while Eddie keeps an eye on Clark. Meanwhile, Linda Ward, an operator for a remote-controlled jukebox, receives a mysterious call announcing a blackout. She notifies all of the nightclubs in her service area, including Clark's, and they turn out their lights. Clark is then shot in the darkness, and when the lights come back on, Tim's service revolver, which Decker had given to Eddie, is determined to be the murder weapon. Despite Eddie's claims that he left the weapon in his office, Decker tries to arrest him for killing Clark. Eddie escapes and goes to question Linda in the hope that she can recognize the voice that called in the phony blackout report. Linda is wary but agrees to help Eddie in order to clear herself of an accomplice charge. As Eddie continues his investigation, Underwood is murdered, as is Bonnie, a hat check girl who was about to provide Eddie with information about Clark's killer. Eddie intimidates Dizzy, one of Clark's henchmen, into taking him to the warehouse where Tim was shot, and while he checks out the location, Linda calls Decker for help. When she hears his voice, however, Linda recognizes him as the man who called in the blackout report. She rushes to the warehouse to warn Eddie, and as he and Decker struggle, Eddie realizes that the policeman was Underwood's partner in the black market ring and that he killed both Clark and Underwood. The police round up Decker and the rest of the gang, and soon after, Eddie and Linda plan their wedding.