From 2003 to 2004, in the span of less than a year, Yoo Young-chul murdered a total of 20 people in various parts of Seoul. Among his victims were wealthy elderly people, masseuses and young women. The sheer number of brutal murders he committed, the brutal killing methods he used, and the grotesque mutilation of the bodies were horrific and unprecedented. This docuseries tells the story of the hunt for this serial killer