Ma Dongsheng (Zhang Guoqiang), a laid-off worker, robbed a "black shop" in a mask because his daughter Ma Jin suddenly fell seriously ill. The owner of this shop, Li Bing, had raped Ma Dongsheng's apprentice in the past, and the criminal police captain Yu Chao (He Bing) in charge of the case was an acquaintance. However, this case brought out a corruption case and a major drug manufacturing and trafficking case. Li Bing's brother-in-law, Deputy Mayor Chen Zitao, tried every means to cover up the truth and even created a farce to make people take the blame. Unexpectedly, Ma Dongsheng did not escape. He revealed the conspiracy to Yu Chao in an anonymous letter and promised that he would surrender himself. As the case was solved, Yu Chao realized that the suspect was Ma Dongsheng, and also found out that the cause of Ma Jin's illness was actually caused by a "human experiment" by a drug manufacturing and trafficking gang. Tan Jiping, deputy director of the Municipal Public Security Bureau controlled by Chen Zitao, acted as a "protective umbrella". However, Yu Chao's dedication to duty also moved Ma Dongsheng, and he chose to surrender himself. This was also the last chance Yu Chao left for him.