Infernal Affairs II

Meanwhile, the police under the command of Inspectors Wong (Anthony Wong) and SP Luk (Hu Jun) have been placed the on the highest alert. A bloodbath is bound to take place.

To everybody's surprise, the ultimate winner in this scramble is a most unlikely candidate: Kwun's son Hau. An accountant in training, Hau has concealed his cunning ruthlessness under a self-effacing. Almost effortlessly, he manages to restrain all the other Triad bosses to become the new kingpin.

To watch over Hau's every step, Wong sends rookie Yan (Shawn Yue in the role played by Tony Leung in the original Infernal Affairs) as a mole to infiltrate his organization. It turns out that Yan is actually Hau's half-brother who has severed all ties with his father. Inside Hau's organization, Yan befriends Keung (Chapman To), one of Sam's underlings. Meanwhile, in order to strengthen his position, Sam has sent a young subordinate Ming (Edison Chen in the role played by Andy Lau) to enroll in the police cadet academy.

Three years have gone by. Yan has become a trusted member in Hau's organization while Ming has risen up to the top ranks in the police force thanks to information supplied by Sam. In the meantime, Hau has become more ambitious than ever. He sees to it that all the other Triad bosses are taken down at the same time. Even Sam is targeted for elimination in Thailand.

Hau has found out that in order to help Sam advance in the Triad world, Sam’s girlfriend Mary (Carina Lau) has colluded with Inspector Wong years ago to assassinate his father. When Ming learnt that Mary, whom he has a secret crush since time immemorial, is in grave danger, he tries his utmost best to rescue her...

In 1997, Sam suddenly makes a surprise comeback in Hong Kong. It turns out that he has survived Hau's assassination attempt and has been hiding with Keung in Thailand. Wong now tracks him down and convinces him to come back as a witness against Hau…