Dr. Pickerbaugh goes on tour with his health reforms and is well known all over America. He is so popular, in fact, that the Republicans nominate him to run for congressman. Martin is shocked and told that he will have to take over while Pickerbaugh i s away campaigning.
While Pickerbaugh is away and Martin is running the health department, Martin is called a tyrant. Martin is not aligned with the unions, and he discovers strep infection in the udders of three cows. Because of his discovery, Martin wants to close down the Klopchuck Dairy. Most people, including Pickerbaugh, Irving Watters, and of course Klopchuck himself are against the closure. Another doctor reinforces Martin's opinions, but the town remains upset about the closing of the dairy.
Martin meets Clay Tredgold, the president of the Steel Windmill Company, while he is conducting an inspection of the premises. Tredgold takes a liking to Martin and invites him and Leora to dinner. Before the couple knows it, they are taken into Tredg old's circle of aristocracy as their "poor relations," and are attending get-togethers with the group, which soon becomes known to the reader as the "Ashford Grove Group," given that they are a group of about twelve families that live in the Ashford Grove section of town.
Pickerbaugh has planned a Health Fair in which the whole city participates. There are all kinds of booths, and in one, for example, the "anti-nicotine" woman injects cigarette paper into rats and shows how they die because of it. Martin is also asked to p lay a part and work in a fake laboratory, a stage-set of sorts, in order to show the civilians how such a thing is done. Leora is his "fake assistant." Everything is going well until disaster begins to strike.
First, the Eugenic Family, who is conducting one of the booths, turns out to be, according to the policeman who discovers it, the "Holton Gang," known for selling liquor to the Indians and other crimes. Then, on Saturday, the youngest of the Gang has an e pileptic seizure, and a fight breaks out between the "anti-nicotine" woman and the "anti-vivisection" woman. The "anti-vivisection" woman accuses the "anti-nicotine" woman of being a murderer. Furthermore, the fireman in charge of the "Clean Up and Preven t Fires" exhibit accidentally drops a match into the "Clean House" and starts a fire. Pickerbaugh manages to calmly lead the people away from the site and stop the hysterical stampede that was created as a result of the flames. Meanwhile, Martin and two o thers put out the flames. The next day, Pickerbaugh is proclaimed a hero because it was said he had taught the city a lesson and had prevented hundreds of deaths. All of this publicity is good for Pickerbaugh's vague campaign.
While Pickerbaugh is campaigning for congress, Mayor Pugh is running for re-election. Pickerbaugh tells Pugh that, if he wins, he must elect Martin to his current position as Director of Public Health. Soon enough, Pickerbaugh has won the election and is off to Washington, taking Orchid with him and ending Martin's pining after the girl. Although the mayor had agreed to Pickerbaugh's request, it is a struggle to appoint Martin, until Tredgold steps in, pulls strings, and Martin is appointed as Acting Dire ctor.