- [Narrator] As Burnham and Olmsted turn swamp into spectacle, anticipation swelled across America.

Chicago drew them in.

Capitalists, dreamers, and schemers.

- Everybody was coming to Chicago.

If you wanted to build a fortune for yourself, this was the place to go.

- [Narrator] Among those who flocked there in the years before the fair was a charming doctor who would become one of Chicago's most infamous killers.

(tense music) H.H.

Holmes.

Born Herman Mudgett, his early life in New Hampshire offered only a faint warning of the depths to which he would descend.

- He was bullied as a child, and his bullies had taken him to the local doctor's office and had presented the skeleton to him, and basically tried to scare him.

He said initially he was scared, but then he became curious and he said that's why he decided to go into medicine.

- [Narrator] Mudgett married, and studied at the University of Michigan.

Classmates recalled his zest for dissection.

Rumors swirled that he robbed graves for cadavers.

- There were stories that he had been used to go out to graveyards at night.

He just barely graduated.

A couple of the professors said that they graduated him out of pity.

Just what you want to hear about your doctor.

- [Narrator] His wife left him, and took their young son back to New Hampshire.

Mudgett eventually headed west under a new alias, Harry Howard Holmes.

He quickly learned that deception was more profitable than healing.

- He didn't really do much practicing in medicine.

Eventually he became a pharmacist in Chicago and then got into wheeling and dealing in real estate.

- He would just go under different aliases.

He would start companies.

He had swindle schemes, insurance fraud.

I mean, you name it, he was into it if he could make money.

- [Narrator] Holmes owned a modest building in a south side neighborhood called Englewood.

With the fair under construction just a few miles east, Holmes saw his biggest opportunity yet.

He set out to build a third floor with more rooms.

A World's Fair hotel.

- He borrowed a lot of money from investors.

He was able to swindle flooring companies, hardware companies.

He took out several fire insurance policies on it, and then lo and behold, right in the middle of the fair, before it had actually opened, that third floor caught fire.

The insurance companies were not fooled for a second.

(tense music) - [Narrator] It was not a hotel in any conventional sense, but the intersection of Wallace and 63rd Street became a place where people, especially young women new to the city, vanished.

- Ned and Julia Connor moved into the building Holmes was operating in Englewood.

They brought their four-year-old daughter, Pearl.

Holmes very quickly started having an affair with Julia.

- [Narrator] The Connors divorced.

Ned left.

Julia stayed behind with her daughter, serving as Holmes' secretary.

- He seemed to have a way of making people like him.

And he charmed everyone.

- [Narrator] On Christmas 1891, Julia and Pearl disappeared, leaving behind an untouched meal, and a cherished doll.

Holmes said they'd left suddenly for a funeral in Iowa.

- After they disappeared from the building, a woman moved in by the name of Emmeline Cigrand.

(mysterious music) - [Narrator] Cigrand had recently moved to Chicago.

Holmes spotted the 24-year-old beauty at an employment agency, and hired her as his secretary.

They took music lessons together.

After rumors spread that Emmeline was pregnant with Holmes's child, she also disappeared.

Holmes said she'd left to get married.

Her trunk was sent to her family in Indiana.

(mysterious music) - It's hard to imagine the energy that this man put into destroying other human beings, all the while being likable, and I think it's one of the great mysteries about Holmes, of how he pulled it off.