Herman W. Mudgett, better known by his alias, H.H. Holmes, is considered America's first-- and most notorious-- serial killer. During the 1893 World's Fair in Chicago, the basement of his house in Englewood, Illinois contained a torture chamber with crematory. Mudgett confessed to killing 27 people, but legends say the number may be in the hundreds. Selzer reveals not only the true story but how the legend evolved, taking advantage of hundreds of primary sources that have never been examined before.