Plot: Mainland CID Officer JIANG ZIDAN (Wang Yang), nicknamed “BULLET”, infiltrates a Hong Kong triad group in an attempt to investigate a cross-border drug trafficking case and encounters Hong Kong narcotics inspector WAI CHUN-HIN (Him Law) and female officer CHAN YUET-KI (Cecilia So). The swift and smart BULLET is favoured by the triad leader WU KOON-YAU (Damian Lau), but he is not aware that CHUN-HIN is the trusted one of the triad’s deputy leader HON LONG (Gallen Lo)