H.H. Holmes and the Mysteries of Murder Castle, Part 1

As a student, Herman W. Mudgett used corpses to commit insurance fraud. In 1886, he moved to Chicago under the alias H.H. Holmes. In 1888, Holmes started constructing a building with secret passageways and an airtight vault. So, what was it for?

World's Fair Hotel, aka H.H. Holmes' "Murder Castle"