A world-renowned painting is stolen during an exhibition. The International Criminal Police Organization assigns Chinese officer Chen Hao to investigate the case. Chen Hao goes undercover as a Hong Kong businessman, facing numerous challenges and dangers as he infiltrates the criminal underworld. The thief, Hu Wei-yi, tests Chen Hao through various means and has his sister, Hu Manman, get close to him. Hu Wei-yi keeps a killer, Black Fox, imprisoned in a basement, who becomes a sexual deviant and assaults Hu Manman. Just then, Hu Wei-yi arrives, and Black Fox threatens them with a gun, forcing the siblings into a compromising situation…