In 1970s Hong Kong, the Independent Commission Against Corruption (ICAC) was formed to bring down the corruption syndicate led by British government officials. One of its top investigators is Senior Investigator Lau Kai-Yuen, who brought down countless corrupted officials. Just as he thought stability and prosperity are within reach, a new era of greed and riches takes him into a new battlefield of corruption.
Hong Kong Customs and Excise Department officers Chow Ching-lai and Cheung Wan-nam share a close mentor-student relationship. On a case involving seized smuggled arms, Ching-lai is sent to take part in a joint operation with Interpol to capture a reclusive arms dealer. However, Wan-nam makes a drastic decision that further complicates the case.
The Yau Tsim Mong area, the core commercial area of Hong Kong, has recently experienced a series of robberies. Many jewelry stores in the area have been ransacked by gangsters. Police unit is given the mission to take the gangsters into a custody, but the operation is not so easy.
Ho Sau, an undercover agent, has been working with Yau, a drug lord, for years, but his job and family are in trouble.
