On the Edge (2006)

After working as an undercover in a triad for 8 years, Sheng finally arrests the triad leader and resumes his duties as a police officer. However, life does not return to normal as he is faced with suspicions colleagues and even trailed by the investigations team. One day, he meets some triad members whom he has earlier befriended as an undercover agent and is forced into a corner when asked to collaborate with them once again.