Set 100 years before the events of Xenosaga Ep.1, Xenosaga: Pied Piper tells the story of cyborg Ziggurat 8 in his former life as human counter-terrorist agent Jan Sauer working for the Galaxy Federation. It centers on Sauer’s team as they track a serial killer known by the hacker alias "Voyager," who stalks and murders his victims, mostly children, inside the U.M.N., or Unus Mundus network, a universe-spanning virtual reality internet. The squad is deployed to the planet Abraxas to investigate these murders and bring Voyager to justice. As Jan carries out his investigations, he meets Dr. Sharon Rozas, and over time, the two fall in love and get married. As Jan's investigation gets closer to unveiling Voyager's identity, it becomes clear that high-ranking officials in the Galactic Federation are connected to Voyager and attempt to shut Jan and his team down. After escaping arrest and finally unveiling Voyager as Erich Weber, a member of his own team, Jan is forced to watch Sharon and her son murdered in front of his eyes and chooses to take his own life rather than be used by corrupt higher powers or be killed by Voyager. His body is reclaimed and recycled, which leads to him becoming the cyborg Ziggurat 8.