A high-class crook gets in trouble with the law.

New York gambling house operator Johnny O'Clock is junior partner in a posh casino with Guido Marchettis and Chuck Blayden, a crooked cop. But Blayden is trying to cut into the casino's profits and warns Johnny not to interfere with his intention of becoming Marchettis' full partner. Blayden ends his relationship with coat check girl Harriet Hobson, then disappears. Later, Harriet is found dead in her apartment, apparently from suicide. Police Inspector Koch begins an investigation.He questions Johnny, Harriet's sister Nancy, who is infatuated with Johnny, and Johnny's associate, Charlie. When Blayden's body turns up in a nearby river, and when it is learned that Harriet death wasn't suicide but murder by poison, Johnny and Marchettis become prime suspects in both cases.To make matters worse, Pete Marchettis discovers that his wife Nelle may be having an affair with Johnny. Out of jealousy, he sends hired gunmen to kill Johnny in a drive-by shooting while Johnny is driving Nancy to the airport. Johnny, now certain that Marchettis has betrayed him, goes to the casino to end their business partnership.—nufs68

Living in comfort in an upscale full service hotel residence with Charlie, an ex-con he's hired to be his flunky, Johnny O'Clock is the hands on junior partner of a casino operation along with Guido Marchettis, Johnny seen as the brains, Guido the brawn and the money with trophy wife, Nelle, on his arms. Johnny receives an unwanted visit from Homicide Police Inspector Koch, who is looking for Police Detective Chuck Blayden, as Koch knows that Blayden is a "business associate" of Johnny's, and as Blayden is in probable trouble in having shot a gambler dead, it publicized as in resisting arrest, but which Koch believes was more likely in relation to Blayden's personal interest in the casino. Johnny receives a second visit from Koch the following day when someone associated to Johnny is found dead in a seeming suicide, indication that a still missing Blayden is also dead. Johnny knows that a lavish gift given to him in the name of love and that he tried to return, he learning unsuccessfully, may be problematic for him with regard to both deaths. In dealing with the suicide victim, Johnny meets chorus girl Nancy Hobson, the two who start to fall for each other. How Johnny tries to get himself out from under the increasing implication that he was the cause of both deaths is affected by Nancy in his life.—Huggo