A carefully planned bank heist by hoodlum Harry Wheeler and his partner leaves a policeman dead and $200,000 stolen. After the police investigation, headed by Lt. Carl Ekstrom, identifies Wheeler as the culprit, Eckstrom assigns detective Paul Sheridan to befriend Wheeler's girl friend, Lona McLane, who has moved into an apartment in town. Paul stages a meeting with Lona and a powerful attraction develops between the two. Paul takes Lona to his apartment for the night, then spends the next several days with her. Later, Eckstrom, Paul and his partner, Rick McAllister, devise a stakeout across from Lona's apartment, and wait for Wheeler to contact her. On Paul and Rick's first shift, Lona leaves the apartment and Paul follows her, only to be startled when she drives to his apartment. He meets her there and she accuses him of having staged their meeting and asks if he is a cop. Paul admits to being a detective, but insists that he has been seeing her for personal reasons. Lona discloses that she is frightened of her involvement with Wheeler and insists that she did not know about his criminal activities until after the bank robbery. Lona asks what would happen to Wheeler if she turned him in, and when she suggests that she and Paul would be happy with the robbery money, he angrily demands she leave. Paul returns to the stakeout room and discovers Rick watching Lona's neighbor, a young nurse, Ann Stewart, whom Rick comes to admire. Depressed over his argument with Lona, Paul grows restless and his increasing exhaustion is noted by Rick and the other members of the stakeout team. One evening when Rick leaves the stakeout room briefly, Paul telephones Lona and asks to meet her on the roof. There he promises to get the money when they apprehend Wheeler, if she will run away with him. Lona agrees and reveals that Wheeler will be contacting her the next day by phone to find out through an agreed upon signal, whether it is safe for him to meet her. The next day, early in Paul and Rick's shift, Wheeler calls, and after Lona gives the signal and departs, Paul has Rick follow her. Intending to capture Wheeler alone, Paul telephones detective Paddy Dolan, who is keeping watch in a squad car outside, and is disturbed when there is no answer. Outside, Paul sees Paddy leaving a nearby bar. Paddy is guilt-stricken over his lapse, and as he apologizes, the detectives notice Wheeler entering the apartment building. Paul assures Paddy he will cover for him, and the detectives arrest Wheeler on his way out. When Wheeler leads them to his car, Paul shoots him while Paddy is examining the bag of money, then claims that Wheeler was about to attack Paddy. Although anxious, Paddy grows suspicious when Paul suggests they hide Wheeler's body, and refuses to give Wheeler's car keys to Paul. Later, as arranged with Lona, Paul slips into her apartment and waits for her call to assure her all is well. Upon leaving her apartment, however, Paul runs into Ann, then heads back to the stakeout room. Rick returns shortly, followed by Eckstrom, who sends Paul out on a pretext. Eckstrom informs Rick that he telephoned the stakeout room for an hour and received no answer. Rick admits that as he was leaving to trail Lona, he noted Paddy's empty car and saw him going into the bar and suggests that Paul may be covering for the older detective. Meanwhile, Paul finds Paddy, and instructs him to move Wheeler's car so it will not be discovered too soon. Certain that Paul is after the money, Paddy refuses and, pulling his gun, declares his intention to report his failure to Eckstrom. When Paddy's car phone rings, Paul lunges for the gun, which goes off, killing Paddy. Distraught over Paddy's death and the discovery that Wheeler's car has disappeared, Paul then telephones Lona for another meeting on the roof. Suspecting Paddy moved the car nearby, they spot it parked in an alley. Meanwhile, Ann, who knows about the police presence, runs into Rick and informs him that she saw a man coming out of Lona's apartment, who Rick assumes was Wheeler. Later, as Lona takes Rick on another fruitless drive, Paul moves Wheeler's car and dumps the body, which is discovered just as he returns to the stakeout room. Eckstrom and Rick then question Lona, who reveals nothing. When Ann spots Paul heading toward Lona's apartment, she reports it to the police. Realizing Ann has recognized him, Paul picks her up at gunpoint, then with Lona, leaves the building. Eckstrom and Rick receive Ann's report as Paul goes outside and notices two squad cars around Wheeler's car. He sends Ann to the trunk to retrieve the money, but Rick and another detective intercept her and have a shootout with Paul as Lona watches in dismay. Lona is arrested and a wounded Paul apologizes to Rick, who escorts Ann back to her apartment.
