The story of the pioneers of law and politics continues. This time, the protagonist is Bu Guodong (played by Lai Yiu-cheung), a senior chemist in the Forensic Department. Guodong, known as the "Human Encyclopedia", is knowledgeable and has been learning all the time. He and Zhong Xuexin (played by Maggie Cheung), a senior doctor in the forensic department, are not only business partners, but also friends in life. They study the difficult and miscellaneous matters at work together and confide in each other about the troubles in life. Xuexin's friend Ling Qianer (played by Kate Tsui) works in the Xilong Jiu Heavy Case Team. As a senior inspector, she is very skilled and is a good partner with Sergeant Li Zhanfeng (played by Ron Ng). The Forensic Department, the police, etc. often need to cooperate because of various cases, and it is with their joint efforts that one difficult case after another is solved. Bu Guodong and his wife Zhou Yifei (played by Nancy Wu) ended up divorcing because of their different ideas, and his feelings for Xuexin also grew day by day. Xuexin's tragic childhood experience made them turn their attention to new cases...