Chapter 44 marks a history-making day at the fair. In a promotional effort, Millet designates October 9 as Chicago Day, and Harrison requests that businesses shut down in honor and celebration. Chicago Day puts the fair at record attendance; approximately 750,000 people attend in a single day. The outpouring brings the fair out of debt, and the chapter closes with Burnham and other stakeholders celebrating financial success and planning for the closing of the fair.
As Millet schemes to make the closing day ceremony a big attraction, many other key builders reluctantly leave the fair. Holmes also determines the time is right to exit Chicago: Those to whom he owes money have been investing more interest in collecting their due and further inquiring about some of the missing women.
Holmes sets fire to the top of his building and files an insurance claim. An insurance company investigator finds that Holmes has a long history of debts to other people. The investigator informs these businessmen about his discoveries. The lenders collectively hire a lawyer, who calls a meeting with all the creditors and Holmes.
Holmes doesn't know that all of the businessmen to whom he owes money are going to be present at the gathering. He thinks he's meeting with just his lawyer, so Holmes is thrown off guard. Holmes tries using his charm to maneuver his way out of the situation, ultimately fleeing out of fear that his ploy will fail this time. Holmes takes off to Texas with Georgiana Yoke. He plans to use Minnie's estate funds to build a structure much like the one he erected in Chicago.
Chapter 46 ushers in the end of October, and Millet continues to prepare for the fair's rapidly approaching closing day ceremony. A few days before the scheduled closing ceremony, Mayor Harrison hosts several mayors from across the country for American Cities Day. Harrison delights the city by announcing his engagement to the young woman he has proposed to.
After a long, successful day hosting his mayoral guests, Mayor Harrison retires home to have dinner with two of his children. His dining is interrupted by an uninvited guest at the door; Harrison's maid politely asks the visitor to return a bit later. Later, Prendergast comes back to shoot and kill Mayor Harrison. Not long after, Prendergast turns himself in to police, with recently fired revolver and simple explanation for the assassination, "He didn't live up to his word." Instead of Millet's elaborate closing ceremony, the fair's last day serves as a memorial service for Mayor Harrison, with over 200,000 people in attendance.
Chicago becomes a changed place after the fair's closing. Without the exposition providing jobs and bringing consumers to Chicago, the economy shifts radically. More and more people are losing jobs and unions are striking. President Cleveland even sends troops to Chicago the year following the closing of the fair, and much of the fair is illegally set ablaze.
These four consecutive chapters bring closure to the 1893 Chicago World's Fair. Part III also presents the climax of the novel. Key players in the fair's construction and H.H. Holmes all make their exit from Chicago. Prendergast's purpose in the novel is finally clear: His assassination of Mayor Harrison serves as the climax or high point of action in the novel.
In Chapter 45, Holmes again employs his skills of charm and manipulation to get out of a difficult situation. However, this chapter serves as a turning point for this plot line; the reader actually sees the authorities closing in on Holmes as they begin to uncover his criminal activities. Thus, Chapter 45 sets up Part IV of the novel.
Three consecutive chapters — 45, 46, and 47 — employ the literary technique of irony. In Chapter 45, the evil H.H. Holmes leaves Chicago. Ironically, in Chapter 46, Holmes's exit hasn't eliminated all the wickedness in Chicago, as evidenced by Prendergast's assassination of Mayor Harrison. Chapter 47 puts the fair's impact into perspective as Chicago suffers soaring unemployment, increasing crime rates, and rioting after the fair closes.
Imagery of fire in Chapters 45 and 47 is also of note. In Chapter 45, Larson uses the image of fire in a similar manner as he's employed in previous chapters. Although taking the lives of many firemen, the fire in the Cold Storage Building in Chapter 40 does have a positive effect: increased fair attendance. Along the same lines, the fire on the top floor of the World's Fair Hotel in Chapter 45 also produces a positive outcome: the beginning of the downfall of the devilish H.H. Holmes. Larson uses the image of fire in a different sense in Chapter 47. Throughout the novel, fire symbolizes death and destruction. Appropriately, then, the fair comes to its demise as arsonists destroy what is left of it a year later.