The Scarlet Mansion by Allan W. Eckert
A novel based on the life of Herman Mudgett, alias Dr. Henry H. Holmes, one of the most notorious serial killers of all time, who, before the turn of the century, murdered no less than 133 people. A fascinating view of this dangerous person from the time of his first murder, when he is only 12 years old, to his adult years when he has built a huge, 105-room mansion in Chicago, with most of the space devoted to chambers for torture and death. For many years he has a partner in crime named Ben, but when Ben dies under mysterious and very suspicious circumstances, Philadelphia police detective Frank Geyer is assigned to the case and doggedly sets out to track down the serial killer. As Mudgett/Holmes flees, taking with him Ben's wife and children, it becomes a race to see if Detective Geyer can apprehend him before he kills the other members of Ben's family.