It is June 1895, and over two years has passed since the opening of the fair. Chapter 48 introduces a new character, detective Frank Geyer of the Philadelphia police department. Geyer, a seasoned detective, has a new assignment: H.H. Holmes. H.H. Holmes is in Philadelphia police custody for faking the death of Benjamin Pietzel, an act considered insurance fraud. However, as the detective researches the case, Geyer suspects H.H. Holmes has done far worse.
Geyer knows that Holmes had run the World's Fair Hotel in Chicago during the exposition. He also knows that at the end of the fair, Holmes moved to Texas, and then traveled around a bit, staying in cities such as St. Louis and Philadelphia. It was in Philadelphia where Holmes supposedly fakes Pietzel's death and collects $10,000 from an insurance company. He then goes to Pietzel's wife Carrie and convinces her to let Holmes take her three children, Alice, Nellie, and Howard, to see their father, who's in hiding. Geyer believes that Holmes actually killed Pietzel, and his real assignment is to find Pietzel's children. Holmes claims that they are in England with Minnie Williams. Besides information from interviews with Holmes, the only other evidence Geyer has in hand is a series of letters from Alice and Nellie Pietzel to their mother, letters that outline some of their travels with Holmes.
Geyer uses the letters from Alice and Nellie Pietzel to retrace Holmes's steps, hoping that the trail of the suspect's travels will unveil some information. Geyer's search takes him to Cincinnati, Indianapolis, Chicago, and Detroit, where he finds the hotels and rentals that Holmes and the Pietzel children had occupied. In each city, Geyer picks up new information along the way. In Indianapolis, Geyer discovers that Georgiana Yoke, Holmes's fiancée at the time, had been traveling with Holmes but that Holmes had somehow managed to keep her and the children unaware of each other. His search then takes Geyer to Chicago, where he ironically doesn't collect much information about Holmes. Detroit is the next destination, where the Pietzel girls' letters seem to stop. In Detroit, Geyer discovers that Holmes was moving three separate parties of travelers from place to place, including Carrie Pietzel and her other two children.
One purpose of this chapter is to introduce a new character and protagonist, Detective Frank Geyer. Immediately, the reader is drawn to Geyer as he begins to accomplish what someone in Chicago should have discovered long ago, the extent of Holmes's evil.
Chapter 48 also functions as a way to catch up with Holmes's increasingly bizarre and deviant activities since he left Chicago. While in Chicago, Holmes frequently uses letters to keep creditors and suspicious family members of his victims at bay. In this chapter, ironically, letters from the Pietzel children are what ultimately help Geyer uncover the truth about Holmes.