The book begins aboard the RMS Olympic on April 14, 1912, the day its sister ship, the Titanic sinks. On the Europe-bound Olympic are famous architect Daniel Burnham, his wife Margaret, and his daughter and her husband. Burnham is not in good health and is suffering from a foot injury, a byproduct of his diabetes. Suddenly, Burnham decides to send a wire message to Francis Millet, famous painter, dear friend, and colleague who helped Burnham build the 1893 Chicago World's Fair. Millet is traveling aboard the Titanic. However, the ship hand sent to wire Millet the message returns to tell Burnham that his mission was unsuccessful. Burnham demands an explanation.
While the ship hand is off seeking answers for Burnham, the architect's mind travels back to the 1893 Chicago World's Fair and the people who played an intricate role in the creation of such a magnificent exposition. Most of the key contributors to the fair are no longer alive; survivors include Burnham, Millet, and Louis Sullivan, another architect whose firm helped build the fair. The ship hand comes back with a limited explanation for why Burnham's message was thwarted. All the ship hand can tell Burnham is that the Titanic, the ship on which Millet is a passenger, has been in an accident.
The prologue introduces one of the main characters and protagonist, Daniel Burnham, and his connection to the primary setting, the 1893 Chicago World's Fair. Author Erik Larson uses a flashback, while Burnham awaits answers from the ship hand, to deliver important background information about the setting. This flashback provides a brief description of the fair and events and people who made it so great. There is also mention of the evil that simultaneously existed with this greatness at the time of the fair. The author is setting the organizational pattern for the rest of the novel: the juxtaposition of the themes of good and evil in events surrounding the lives of Daniel Burnham and serial killer H.H. Holmes during the 1893 Chicago's World Fair.
The flashback also gives a small taste of the nonlinear structure followed in the rest of the book. Chapters bounce back and forth between the lives of Daniel Burnham and H.H. Holmes during the time of the fair. While the novel somewhat follows a chronological order in telling the two men's stories, the narrative is frequently interrupted by flashbacks, quick shifts from scene to scene, and quotes from Larson's research that often serve as commentary on events as or after they happen in the novel.
The prologue also sets the tone of the novel and foreshadows the many deaths to come. As Burnham nostalgically remembers the fair and his friend Millet, one of the few fair creators still alive and healthy, Millet probably is dying aboard the Titanic. In Millet's impending death, the tragedy and death surrounding the fair is foreshadowed, and the tone of a large part of the novel is set.
Stylistically, this novel follows the lead of many classic works of literature — such as Harper Lee's To Kill a Mockingbird and S.E. Hinton's The Outsiders — by beginning where it ends. The novel begins and ends in 1912 aboard the Olympic, much later than the bulk of the setting of the novel, the years surrounding the 1893 Chicago World's Fair. By doing this, the author creates a full circle of events, a stylistic effect mirroring the works of great writers such as Lee and Hinton.