Hoi (Nick Cheung) was an undercover cop. He was the reason of the arrest of mob head Dark (Francis Ng), who killed himself in jail. After returning to normal life, his experience was hard to bear. In the mob circle, he was regarded as a traitor. In the police circle, his loyalty was questioned. His relationship with her ex-girlfriend changed because they were standing on different sides of the law…

The theme of the story is about the value of being an undercover. As pointed out at the end of the film, more than 50% of the undercover cops quit within 3 years after returning to the police force in real life. This is exactly what Hoi faced: distrust from the police and rejection from the old mob friends. In the end, the film posed the question: Is it worth to be an undercover for justice?

Some people raised the question of whether the film copied the ideas of the Infernal Affairs series. The director of the film Herman Yau claimed that the ideas came actually before Infernal Affairs. In any case, I do believe the film is well made. The story is coherent and the characters are well-designed. It has been a while since I last praised a Hong Kong film and I have no hesitation to show my admiration to this film.