Former detective Shen Mo suffered from schizophrenia due to the stimulation of his daughter's fall from a building three years ago, splitting into a calm reasoning "detective personality" and a paranoid and vindictive "avenger personality". In order to conceal his condition, he disguised himself as a private detective to take over the case. However, when investigating the serial corpse-burning cases, he discovered that his daughter's favorite iris appeared at the scene of each case. Su Heng, a gentle library researcher, intervenes as an expert in ancient book cryptography and gradually uncovers the truth sealed in Shen Mo's memory - the death of his daughter was not an accident. Shen Mo's "Avenger Personality" begins to take over. Between Su Heng's healing and the constraints of the law, he must decide whether to complete self-salvation or completely become a black man...
