Rocky Barnes and Daniel Purvis, two policemen working the night shift, have been partners since they served in the war together. Although Rocky believes that even criminals have some good inside, Daniel is more cynical. Daniel is particularly anxious to capture petty criminal Ritchie Garris, but is hampered by the fact that the victims of Garris' strong-arm tactics refuse to testify against him. Rocky is more interested in the face that belongs to the sultry voice of the night dispatcher than he is in Garris and soon discovers that the attractive voice is that of Katherine Mallory, a policeman's daughter and the captain's secretary. Rocky and Daniel invite Kate to dinner at Garris' club, and there they spot Leo Cusick, an important mobster from the East. Rocky and Daniel believe that Cusick's presence at the club signals the beginning of a gang war to take control of the city. When the policemen drop Kate off at her home, she tells them there will be no more dates because she does not want to repeat her mother's experience as a policeman's widow. Kate's mother, on the other hand, encourages the men's interest in her daughter by renting them the flat next door. When a man is killed outside Cusick's loan company, the police converge on the building. Rocky and Daniel arrive first and chase Garris and his henchman, Joe Quist, as Kate listens over the radio. After the two policemen catch the criminals, Kate realizes that she has fallen in love with Rocky and agrees to marry him. Garris is found guilty of murder and as he leaves the courtroom, threatens revenge on Rocky and Daniel. Later, Garris escapes from jail and carries out his threat, killing Rocky. Determined to avenge his partner, Daniel sets up a constant watch on Garris' girl friend, Terry Romaine, refusing to believe her protests that she is finished with the gangster. When Garris shows up at Terry's apartment, she tells him that she wants nothing to do with him. In order to prevent her from leaving him, Garris then takes Terry's young neighbor Kathy hostage. Alerted by a listening device that has been planted in Terry's apartment, police surround the building, but Garris spots them and holds Kathy out the window, threatening to drop her unless the police leave the area. Daniel offers to try to reach Garris without harming Kathy. Once he is outside Terry's apartment, Daniel uses tear gas and shoots at Garris. Garris returns his fire, but Terry takes the bullet that was meant for Daniel. Daniel then kills Garris. Terry's unselfish action alters Daniel's belief that people do not change for the better, and Kate expresses her approval of his new attitude.