Captain Bill Dugan is an old-fashioned, two-fisted policeman who has used strong-arm methods for twenty years and therefore has no patience with the newer scientific methods of law enforcement. Inevitably, Dugan clashes with Danny Blake, a rookie who believes in the new methods and is also in love with Dugan's niece, Kathleen Burke. The precinct is being plagued by a series of unsolved jewel robberies, and Danny determines to resolve them by using scientific techniques. Tracing a heelprint that he has found at the scene of a robbery, Danny identifies Charles Bixby as one of the gang. Bixby is brought in for questioning, but later released because of insufficient evidence. Following Bixby to a jewelry store owned by Banford, Danny calls Dugan to make an arrest, but Bixby disappears before the captain arrives, and Danny is suspended from the force for harassing Banford. Enlisting the aid of Grazzi, another officer, Danny investigates Banford's establishment and finds evidence that links the jeweler and the robberies. Danny talks Bixby into turning state's evidence, but the thief is murdered by one of Banford's men before he can testify. Before dying, Bixby tells Danny that Banford is really Max Stockton, a jewel thief who supposedly died in a prison fire, and warns him about a planned robbery the following night. As a result of the Bixby fiasco, Dugan is demoted and Danny jailed for impersonating an officer. In his cell, Danny scuplts a wax model to prove that Banford is really Stockton, and when Kathleen brings her uncle to see the model, Dugan realizes that Danny is right. Danny is then released from jail and joins Dugan as they arrest Banford in the middle of a robbery. With Banford's arrest, Danny is vindicated, and Dugan finally admits that science can win over brawn.