Forensic doctor Chen Yu's sister Chen Tang died tragically, and the murderer was at large because the evidence chain was tampered with. Chen Yu was transformed into a mechanical prosthetic body and sneaked into the underground world as a non-human to hunt down the murderer. Jiang Yan, a veteran detective who was investigating the new serial case, discovered that all the clues pointed to his former best friend. When the murderer commits another crime in human skin, Chen Yu is on the verge of going berserk and is awakened to his sanity by a young street boy. Together with reporter Ding Lan, he uncovers the bloody transaction network between police top executive Wei Donglai and underground banks - but the sequelae of his transformation are devouring the last of his humanity.
