Moose Malloy, a brutish prison escapee, forces Goldie Locke to drive him to Club 13, a posh nightclub, where Moose hopes to be reunited with his old girlfriend Velma. After bashing his way into the club and not finding Velma, he kills the club manager and orders Goldie to drive him away from the club. When Gay Lawrence, an amateur sleuth and Goldie's boss, arrives at the club, he learns that Moose is the suspect, because the manager died of a broken neck. Police Inspector Inspector Mike O'Hara arrests Goldie as an accomplice, but after questioning, Goldie is released.
Lawrence and Goldie head out to the house in Brooklyn where Moose is hiding. Pretending to be drunk, Lawrence enters the house while Moose makes a getaway in Goldie's car. In the house, Jessie Florian is on the telephone, shouting hysterically and demanding protection from Moose. Jessie is told to send Moose to a certain address. Jessie tells Lawrence that Velma is dead. Seeing the address, he knows where Moose will be.
When Lawrence returns to his apartment, a call from Quincy W. Marriot to deliver ransom money for a stolen jade necklace sends Lawrence to a deserted graveyard. Marriot ambushes him, grabs the detective's gun, and shoots him, but, in turn, is shot by an unseen assailant who makes his escape.
Seeing Lawrence is still alive, Reporter Ann Reardon, who has been trailing him, helps the detective to his feet, learning his gun was loaded with blanks. Lawrence searches Marriott's coat pockets and finds a business card from Jules Amthor, at 415 Morton Avenue, the address where Moose is going.
Lawrence asks Ann to track down the stolen necklace that belongs to socialite Diana Kenyon. He makes a date to meet Diana at the Swan Club later that night, while Goldie heads to see Amthor. When he enters the house, Moose arrives, but the lights go out and gunfire erupts. When the lights are back on, O'Hara enters and discovers Amthor's dead body. Lawrence and Goldie return to Jessie’s house, to find her dead, with a broken neck.
Working on clues left at Jessie’s house, Lawrence is convinced something is wrong with the theory that Moose is a murderer. Returning to his apartment, he meets Ann, who, after spending the day at police headquarters, learns the police think that Moose pleaded guilty to manslaughter to protect Laird Burnett, the owner of the Swan Club. Diana goes on a drive with Lawrence who has already guessed her true identity, as Velma. When she tries to kill Lawrence, Moose, who had been driving, turns on her, but is shot and killed. Ann arrives in a backfiring car that gives Lawrence a chance to disarm Velma.
Ann gets her first big scoop, uncovering a sordid blackmail scheme that involved Velma, Burnett and Marriott. Just when Lawrence is about to leave the squad room to meet his fiancée, a glamorous woman asks for his help and he comes to her aid.
