When Lui To (Bosco Wong) was just a child, he and another girl, Yan Yuet-Mui (Shirley Yeung), were kidnapped on the same day by an organization which captured children in order to sell and exploit them for labour.

Lui To and Yan Yuet-Mui were able to escape with the help of Lo Sei Leung (Kingdom Yuen), a woman who worked for the organization but had wanted to leave for a long time.

Lui To's adamantly honest ways and naive sense of justice gets the better of them when Yan Yuet-Mui ends up with a fever; since Lui To had given the last of their money to a beggar, they accept medicine from a seedy medicine seller which leaves Yan Yuet-Mui mute.

Many years later, Lui To becomes a police officer while Yan Yuet-Mui attends school and plays the violin.

In order to protect Lam Ping, Lui To investigates Tsui Fung and discovers his dark past.