A Tai Chi master must teach his son how to kick some serious butt, after the son is bullied by a karate master.

After suffering life changing injuries in the line of duty, bomb disposal officer Fung turns his back on the police. But when a devastating series of bombings sweep Hong Kong, the police suspect their former ally may be involved after he is found unconscious at a crime scene. Now faced with memory loss and recalling only fragments of his former life, Fung sets out to uncover the truth and find out who he really is.

Chen is a dedicated social worker who has allowed her job to dominate her personal life. Inadvertently, she neglects her devoted husband Lo-Wei and their young son. Although he dislikes his wife's patients ("they're just street trash"), Lo-Wei is tolerant of his wife's workaholic situation and he takes the opportunity to develop a strong unity with his son, Chia-Pu. Then, Lo-Wei's sister offers to babysit the child while the parents respond to an emergency case. While they're gone, one of Chen's "delinquents" breaks into the house and rapes the sister. During the assault, baby Chia-Pu climbs out of the window and falls to his death. Lo-Wei is over-the-edge with grief. His brain snaps. He withdraws into himself, except at night when he stalks the "street trash," gruesomly killing them...

Four carefree lovers in Hong Kong enjoy their youth while danger looms on the edges.