The ICAC received a real-name report from the informant Liao Yuping (played by Chrissie Chau), reporting that the second-generation rich man Cao Yuanyuan (played by Raymond Lam) who was in prison was suspected of bribing the prison supervisor Shen Jiquan (played by Patrick Tam) and the correctional officers. Chief Investigator Luk Chi-lam (played by Louis Koo) decided to go deep into the tiger's den and go undercover in the prison. In prison, the two major gangs of former police superintendent Huang Wenbin (played by Lam Ka-tung) and Cao Yuanyuan, who were sent to prison by Luk Chi-lam, were at loggerheads. Luk Chi-lam took the opportunity to get close to Cao Yuanyuan to gain his trust. At the same time, the ICAC Chief Investigator Cheng Deming (played by Kevin Cheng) and the Director of the Operations Department of the Domestic Anti-Corruption Bureau Hong Liang (played by Ding Haifeng) outside the prison also joined forces with the mainland and Hong Kong to work together and finally successfully cracked a major corruption and bribery case.