After she finishes her shift as a carhop, Ruby Cain receives a ride home from her sweetheart, narcotics dealer Max Taylor. At Ruby's and Joyce's apartment, roommate Joyce Harper, an ex-army nurse, tells them that she has quit her job and will be looking for a new one. Later, at a bar, Max leaves Ruby alone while he speaks with his boss, bar owner Joe Calla, in the back room. When a drunken man harasses Ruby, two police officers are called to arrest him. Max notices the officers in the bar and decides to slip quietly through the back door, leaving Ruby without a ride home. When one of the officers, Sgt. Ann Rogers, realizes that Ruby is stranded, she gives her a lift home. At the apartment, Joyce mentions that she is looking for work, so Rogers encourages her to join up with the police force. Max learns of Joyce's new career and leaves town with Ruby, so Rogers files a missing persons report. A short time after Joyce has graduated from the police academy, a motorcycle officer named Gates stops her for a traffic violation. Gates mentions that he has been transferred to plainclothes detail, effective the next day. The next morning, when Joyce reports to work, she is paired with Gates. After Joyce takes part in a gambling house bust, Gates is impressed and asks her for a date. Later, Joe and bartender Sam Chase are charged with murder. Soon, Capt. Parr of the Narcotics Bureau assigns Joyce, who has become engaged to Gates, to find Bessie Collier, the wife of a suspected narcotics dealer. Joyce tracks down the woman and is surprised to find Ruby living at Bessie's address. Ruby tells her that she and Max went to Chicago, and were married. Some time later, Ruby fell ill and Max gave her some pills to take. Ruby took the pills to the doctor, who told her that they contained illegal narcotics. Soon after, Max shot a man, and after the couple was forced to leave town, Ruby discovered that she was pregnant. After being caught and put in jail, Max learns of Ruby's pregnancy, but refuses to lead Parr to his supplier. Joyce decides to go undercover and, using the alias "Lola Dallas," arranges the purchase of $100,000 worth of dope from a dealer named Leo Pawley. Later, Max agrees to help the police and leads them to the home of Richard Cott. When Cott's butler sees Max, whom he knows to be incarcerated, he guesses that Max is working with the police and reaches for his gun. While another officer grabs the butler, Gates sneaks into a room filled with Cott's dope stockpile. Joyce follows him inside, and accidentally drops her flashlight, alerting the dealers, who grab Gates. After police backups arrive and arrest the dealers, Joyce and Gates kiss.