Senior Criminal Intelligence Inspector Cheuk Hoi (Michael Miu) appears in Bangkok, Thailand, where he obtains important intelligence: Nine Fingers Qiang is engaged in drug transactions with Thai Ni Kun. After investigation, it is discovered that the Jiyun Gang killed Ni Kun and traded with Nine Fingers Qiang. In order to find evidence of Jiyun Gang's crimes, Cheuk Hoi and his undercover agents sneaked into the gang's hideout and were discovered by PakKey's capable subordinate Le Shaofeng (Pakho Chau), who fought with them. After escaping, when Cheuk Hoi and his group were about to leave Thailand and return to Hong Kong, a huge explosion occurred, and all the undercover agents except Cheuk Hoi were buried in the sea of fire. Heartbroken Cheuk Hoi faced suspension after returning to Hong Kong and became depressed. At the same time, the largest Hong Kong gang Cheung Hing had an internal fight. The new leader of Cheung Hing, Wei Dexin (Moses Chan), took vigorous measures to eliminate the senior leaders of the gang, including Tan Huanxi (Hui Shaoxiong). However, Tan Huanxi was an undercover agent who had been lurking in Changxing for a long time. Faced with this situation, he once thought about asking the Handler for help to be transferred back to the police force, but his wife suddenly met with an accident and died tragically at the hands of triad members, which made Tan Huanxi completely fall into the underworld.