In the early 1970s, when the Independent Commission Against Corruption had not yet been established in Hong Kong, corruption was rampant and people were living in poverty. Police Sergeant Wong Yat-chung (played by Ti Lung) was upright and refused to go along with the corrupt, so he was not tolerated by other colleagues and was excluded in the police station. In an operation, Wang Yi-chong's subordinate Mo Sen (played by Simon Yam) even shot him from behind and seriously injured him. At the same time, Hong Kong Governor Murray MacLehose appointed Sir Barry Qu to investigate the corruption in Hong Kong, and his assistant Ma Annie asked Wang Yi-chong for help. After investigation, Wang Yi-chong learned that Mo Sen had injured himself out of helplessness. Mo Sen was actually forced by the situation, so he found Mo Sen and selected a group of elite students in the police academy to start collecting evidence of corruption groups together, launching the first blow to Hong Kong's anti-corruption!