With the outbreak of World War II, the government severely cuts back its allotment of steel and rubber for domestic use, and consequently, automobile theft becomes an increasing problem. In the city of Lawndale, police chief Richard Bryan and assistant chief Joe Kirby discuss the thirty-per-cent increase in automobile theft in their district, which Richard believes is the work of an organized crime ring. Special investigator Edward Jason of the State Motor Vehicle Bureau is sent to Lawndale to investigate this rash of automobile thefts and their possible connection to Richard. Edward goes to work undercover as the sales manager for automobile dealer John "J. C." Thomas, unaware that Kirby is the real police connection to the auto ring, which is led by gangster Lance Merlin. At home one night, the widowed Richard spoils his young son Mickey, with the help of his secretary, Betty Standing, and his bodyguard and chauffeur, Benny. After Mickey goes to bed, Richard tells Betty that, though he cares greatly for her, there can never be a romantic connection between them. The next day, Richard's department finally catches one of the auto thieves, Gordon Finch, but the thief threatens to expose the fact that Richard was once a criminal himself. Later, Richard is abducted and taken to a surprise party to celebrate his third anniversary as Lawndale's police chief. Richard is so touched by the testimonial that he attempts to resign. After the party, Edward drives Betty and Mickey home, and uses the opportunity to question Betty about Richard. Back at the police station, Benny, who knows about Richard's past, offers to kill Gordon, but the police chief refuses his offer. Later, Gordon kills a guard and escapes, and a statewide search for the gangster ensues. Afterward, Richard confesses to Betty his criminal past, but she reassures him that it makes no difference to her. They both, however, worry about Mickey finding out, so Richard decides to resign once more. He confronts a meeting of the city council, which, having learned of his past, accuses him of helping Gordon escape. As evidence, Kirby plays an edited phonographic recording of Richard's earlier conversation with Gordon, which implicates the police chief in the murder and escape. Although Richard is arrested, Edward continues his investigation, which gets its first break when Gordon's getaway car is uncovered. Edward traces the car's battery to J. C.'s dealership, where he finds a pair of shoes encrusted with mud that matches dirt found on the getaway car. That night, while Edward searches J. C.'s records, the automobile dealer returns to his business with Lance. While the investigator watches, J. C. gives the gangster Gordon's payoff money. With Betty's help, Edward then follows Lance to his hideout, unaware that the gangster has set a trap for him. Meanwhile, Benny starts his own, unofficial investigation, which leads him to Lance's chauffeur, Hub Gelsey. Benny kidnaps and tortures the driver in order to learn Gordon's whereabouts. With the assistance of his loyal officers, Richard manages to escape from custody, and he and Benny arrive at the gangsters' hideout just as they are about to leave. Richard and Benny are wounded in the ensuing shootout, but with Edward's help, the gangsters are captured. Edward then goes before the city council to expose both J. C. and Kirby. With Richard, Betty and Mickey reunited, Edward prepares to leave town, but first offers Benny a job as his assistant. Benny declines at first, but after mistakenly walking into the maternity ward while visiting the hospitalized Richard, he goes running after the special investigator.