In 2010, the Senior Inspector of Criminal Intelligence of the Hong Kong Police Force Cheuk Hoi (played by Miao Kiu-wai) went to Bangkok, Thailand, to track down transnational drug trafficking lines with local undercover agents. Who knew that in the process, Pak Key, the leader of the Lucky Luck Gang, and his subordinate Le Shaofeng (played by Zhou Baihao) suddenly intervened and disrupted the plan. When Zhuo Kai and his party retreated, they encountered a well-planned explosion, which caused the lives of other undercover agents to be killed. After returning to Hong Kong, Zhuo Kai was disheartened and intended to resign. At this time, the president of Hong Kong's largest community rose into trouble, and his former comrades faced each other with knives, and a war was about to break out. On the other hand, Senior Inspector Li Ruiquan (played by Zhang Zhaohui) was afraid that the identities of the 5 undercover agents within Changxing would be exposed, so he deleted the undercover files in a hurry.