Synopsis for
Murderer (2009) More at IMDbPro »Saat yan faan (original title)

Ling (Aaron Kwok) is a married self-assured Police Chief Inspector with an adopted 5 year old son who is investigating a cold-blooded serial murder case. However due to the homicide attempt of a fellow inspector named Tai in which Ling emerged unscathed, fellow colleagues are fast becoming aware of Ling's potential involvement. Ling suffered a lost of memory since that incident and cannot recall the events leading to Tai's attempted murder.

As Ling sifts through the clues, he finds that all the evidence is pointing toward himself as the murderer. However ling's belief and unwaivering sense of innocent fuels him to maintain his suspicion and keeps digging. Slowly, together with memory re-collection Ling takes temporary leave of absence and enforces a lockdown mode to safeguard his family. It was during the lockdown that his adopted son confesses to Ling his real identity. He is, in fact, the child together with his mother that was abandoned by Ling's father many years ago. Driven by an early life of pain, humiliation and suffering faced by his mother he vowed revenge and painstaking made his way back into Ling's life as his adopted son. He was able to accomplish this due to a medical condition where his physical stature remains that of an 5 year old. Having shared a bed with Ling's wife, played close attention to Ling's friends he was able to slowly fulfill his revenge and give out orders for the murders which was carried out by an acquaintance that he had met many years ago at a disability center.

Ling's wife was murdered by the acquaintant on the site of their premises to which Ling broke down upon discovery. Ling was able to gather himself to dispose of the murderer and was moments away from carrying out justice on his adopted son until the police arrived and shot him. The end of the movie shows Ling in a mental hospital engraving the words "Revenge upon release" on this left arm and a scene of his adopted son maturely dressed contemplating life without Ling in the backdrop of an ocean.