Herman Mudgett, whose alias was HH Holmes, is believed to have been the first serial killer in America, potentially responsible for as many as 200 murders in the late 19th century. Around the same time, Jack the Ripper famously killed at least five people on the streets of London. In this series, Jeff Mudgett - Holmes' great-great-grandson - tries to prove a controversial theory that Holmes and Jack the Ripper were the same person. Mudgett has spent 20 years researching his ancestor, and he uses that information, combined with 21st-century science and technology, to team with former CIA analyst Amaryllis Fox to launch an investigation that could solve one of history's biggest cold cases.