The episode opened with the story of the post-modern feudal world of Filament, which was destroyed when its sun went supernova. An energy cloud formed where the planet used to be, and its inhabitants, not accepting their untimely fate, became spirits. When the 999 passed through the energy cloud, the ghosts disabled the train and kidnapped Tetsuro. One of the spirits wanted her son to possess Tetsuro, so that he (the spirit) could travel to the destination and receive a mechanical body. (thetvdb.com)