Yeung Bik-sin (Kara Hui) suffers from schizophrenia and almost poisons her son Yeh Chin-fung (Vincent Wong). Yeh Chin-fung is so frightened that he develops a weak but warm personality - Zhu Ji. Yeh Chin-fung, who has a dual personality, is appreciated by the father of criminal investigation, Nie Shan (Philip Keung), and is recruited to join the special case team. Together with psychiatrist Wei Rui-jie (Benjamin Yuen), bomb disposal policewoman You Yan-xing (Mandy Wong), Chief Inspector Kong Ching-fung (Lai Lok-yi), forensic anthropologist Fang Wan-qian (Chris Wong), forensic insect expert Zhang Xiao-man (Shiga Lin) and novel editor Hai-lan (Kik Chi-chia), who is often suspected of being related to the case and needs to be investigated, they fight against highly intelligent criminals with various psychological deviations and solve many thrilling unsolved cases.