The terrorist organization “Argunbia" infiltrated Hong Kong and set off a battle for chemical weapons in Hong Kong. Fan Siu-fung (Moses Chan), the commander of the Special Duties Unit (SDU), was ordered to fight against the terrorists. The SDU are trapped in the ruthless killing of “Wakanbo”, leading to the Special Service Superintendent Chin Bok-man (Joe Ma) to assemble the police elites Cheung Wai-wah (Eddie Cheung), Cheung Ka-hin (Bosco Wong) and Ko Chi-lok (Ron Ng), to form a secret counter-terrorism team: S Team. In the face of many crises, with the assistance of Interpol Hui Chun-fei (Michael Miu), the generations of their grievances and feuds are put aside and they join forces to prevent the spread of the chemical weapon virus in Hong Kong.