The legend says America's first serial killer built a Gothic Murder Castle with gas chambers and trap doors to swallow World's Fair visitors. The truth is stranger: the castle was largely a fraud, and the real horror is how mundane and bureaucratic H.H. Holmes actually was.

This deep dive strips away the yellow journalism to reveal Herman Webster Mudgett, a ruthless con artist who used murder as a practical business tool. We trace his cadaver insurance scams, the real reason his building was a maze, and the cross-country child murders that finally exposed him.

• The castle's confusing layout came from constantly firing unpaid contractors; hidden rooms hid repossessed goods
• Holmes killed liabilities, selling secretary Emeline Cigrand's body as an articulated medical skeleton
• He burned his living associate Benjamin Pi ...