After the Chief Deputy of the Department of Weights and Measures is nearly killed in a car accident engineered by corrupt politician Marty Cavanaugh, he enlists ex-boxer Johnny Cave to take over his position.

Johnny then goes out into the field with his naive partner, Patrick James "Aloysius" Haley, investigating merchants who are accused of using faulty measures and cheating the public.

When Johnny learns that Janet's boss, Abel Canning, has been swindling a local orphanage by sending them half-shipments of food but charging them full-price, he declares that he's going to expose him for the criminal that he is.

Once he realizes that Canning is in an alliance with both the mayor and Cavanaugh, Johnny releases the orphanage story to the newspapers, which angers his fiancee and eventually leads to her breaking their engagement.

Johnny goes over to Burton and punches him in the face, then removes what he thinks is the stolen evidence from his jacket pocket, but instead discovers a check written by Canning.

According to Greene, "the scenes with the ward politicians, the Mayor, the philanthropist, crooks all, are pleasantly phosphorescent with corruption, and so is the admirable climax at the evening party".