Rewind eighteen years and Lam Long-sang (Shaun Tam), Sum King-yat (Joel Chan), Tse Ka-fu (Anthony Ho) and their chums are members of a public housing estate youth septet. They clash with a rascal by the name of Wu Kai-sze, who ultimately collapses and dies. The septet gradually drift apart. They eventually go their separate ways and forget their past. Fast-forward eighteen years and while the police are investigating a traffic accident, they discover Kai-sze's remains. The septet are forced to face up to the disaster they had caused. While the chums are feeling confused, Long-sang is even more perplexed as he and Crime Unit Inspector Yuen Lai-kan (Mandy Wong), who is assigned this human remains case, begin to have affectionate feelings for each other. Meanwhile, Lai-kan's father Yuen Tsun (Dominic Lam) is also covertly unraveling the case and seems to have something to do with the remains. The septet are getting jittery as the truth is surfacing. Who really is the perpetrator?