00:00 H.H. Holmes created a building in Chicago known as the murder castle where many people who entered never left alive, making him America's first serial killer.

02:23 H.H. Holmes had a troubled childhood and early signs of psychopathy, and he engaged in shady activities while studying at the University of Michigan, including robbing graves and defrauding life insurance companies.

04:13 After graduating from Michigan with his medical degree, H.H. Holmes moved to Moros, New York, where he was seen with a boy who later disappeared, leading to rumors of his involvement; he then moved to Philadelphia, where he worked odd jobs and was suspected in the death of a young boy; in Chicago, he married a woman named Belknap while still legally married to his previous wife, and he purchased a pharmacy and had a building constructed.

06:11 In the years following his move to Chicago, H.H. Holmes had multiple affairs and several people, including his mistresses and employees, mysteriously disappeared, while he continued to engage in fraudulent activities and even murdered his accomplice, Benjamin Pitassel, to fake his death for an insurance scam.

08:18 Holmes convinced Pitassel's wife to sign over custody of their children to him and then took them on a trip, but eventually abandoned them and all three children disappeared; Holmes was apprehended in Boston and accused of killing Benjamin Pitassel and his children, but the bodies of the Pitassel girls were found buried in a house in Toronto and the jawbone of the young Pitassel boy was found in a house in Indianapolis, leading to the discovery of the "murder castle" and reports that Holmes had murdered as many as 200 people.

10:19 H.H. Holmes was found guilty of the murder of Benjamin Pitezel and sentenced to death, but many of the stories about the murder castle and torture rooms were fabricated and several of the people he claimed to have killed were later found to be alive.

12:28 H.H. Holmes's body was exhumed in 2017 to confirm his identity, and while the exact number of his murders may never be known, he is considered one of the most heinous criminals of the 19th century.