When Joel Green, head of the Department of Weights and Measures, is nearly killed in a car accident by corrupt politician Marty Cavanaugh, ex-prizefighter Johnny Cave replaces him. Facing a city-wide racket of faulty measures, Johnny fines merchants who are cheating the public and ignores the customary bribes and threats of Cavanaugh's men. The night after he refuses a job offer from Cavanaugh, Johnny is abducted. He wakes up, stinking of alcohol, in the gutter with his hair dyed red. In addition, Johnny is falsely accused of theft. Next, the mayor, in league with Cavanaugh, offers Johnny a high paying job, but he again refuses. When Johnny learns that Abel Canning, the boss of Johnny's fiancée, Janet Henry, has ordered that the matron of the local orphanage, Mrs. Ogilvie, be fired, Johnny visits her and learns that the orphanage has been receiving half-shipments of food. With evidence that Canning has been grafting state funds, Johnny has a newspaper headline printed that implicates Canning. Ex-wrester Burton, posing as a city prosecutor, knocks Johnny out and steals his evidence in order to blackmail Canning. After Canning publicly accuses Johnny of blackmail, Janet breaks their engagement. That night, Canning pays Burton for the key to his apartment, and Canning and Cavanaugh locate the papers just as Johnny arrives. Thanks to Janet's call to the police, the two men are arrested before Canning can burn the evidence, and Johnny presents Janet her wedding ring.