During the a chaotic period of Imperial China, before the unification of the country, there exist two opposing regimes: the Song and Jin. The story focuses on the exploits of the Tin Kei (Phecda) Bureau of the Northern Song. It's a special investigative unit that answers directly to the emperor, who is headed by Commissioner Fung Nam Tin (Lau Kong). With his highly skilled group of constables, Fung Nam Tin was able to protect the realm against criminals and enemies of the state.