In the cities of the near future, strong emotions will leave dangerous "historical residue" in reality. Chen Mo is a professional debris cleaner who follows the rule of "just clean up, don't intervene" and uses technological means to quietly erase these emotional imprints. However, during a seemingly ordinary night mission, he encountered an extremely complex projection of a little girl, behind which was entangled with the fear and despair of adults. When Chen Mo discovers that the residue contains clues to an unreported murder, he must make a choice between abiding by the cold rules and getting involved in the truth - and every cleanup may reveal the city's darkest emotional abyss.
