Sent into a drunken tailspin when his entire unit is killed by a gang of thrill-seeking punks, disgraced Hong Kong police inspector Wing needs help from his new rookie partner, with a troubled past of his own, to climb out of the bottle and track down the gang and its ruthless leader.

A group of thieves break into an industrial complex to pull off a jewelry heist, but stumble upon a hidden laboratory where unorthodox SARS and Ebola experiments are taking place on stolen cadavers, who soon mutate into blood-thirsty zombies.

Fat is a loser in work, and even in the triad gang. Ordered by another gangster, Fat attempts to assassinate the leader of the opposite gang. His mission, undoubtedly, ends in a fiasco. Yet this failed attempt hooks him up with his former puppy love, who is now the wife of mysterious gangster Wind. Meanwhile, when Fat is working at a cyber cafe with his buddy Chu, three young and hot policewomen arrive and think that Fat is a missing undercover cop who suffers from amnesia...

In this prequel to the original, a bloody power struggle among the Triads coincides with the 1997 handover of Hong Kong, setting up the events of the first film.