The murder case at the Sixth Machinery Factory triggered an in-depth investigation by the police. The two suspects Xu Wenguo and Yao Binbin gradually surfaced. The guns they possessed were extremely similar to those found at the scene of the case.In order to interrogate the two suspects, Zhang Xiangdong went to Batu Detention Center in person. According to regulations, the discipline manager Du Xiangdong should have avoided it, but he sneaked into the interrogation room and sat in the corner to listen.

Under Zhang Xiangdong's interrogation, Xu Wenguo and Yao Binbin's life experiences gradually became clear.Although they are not related by blood, they are better than brothers.Xu Wenguo lost his parents since childhood and was adopted by the kind-hearted Yao's mother Cui Lizhen.However, their father Yao Wenwu abandoned his wife and children, leaving Cui Lizhen to raise two children alone.For a long time, Choi Lizhen has been bullied and insulted by Li Chao.Li Chao's arrogance has already aroused the anger of Xu Wenguo and Yao Binbin, and the two sides had had fierce conflicts in the factory workshop.

Although Zhang Xiangdong's interrogation skills were superb, Xu Wenguo and Yao Binbin always insisted that they did not kill Li Chao.The continuous high-intensity interrogation made them exhausted, and Xu Wenguo even cast a look for help at Du Xiangdong.Only then did Zhang Xiangdong notice Du Xiangdong in the corner.

Subsequently, Zhang Xiangdong reported to his superiors about Du Xiangdong's illegal intervention in the case.Director Li asked Du Xiangdong to have a conversation. He used the chess game as a metaphor, implying that Du Xiangdong should pay attention to strategies when investigating the case, and at the same time warned him to act cautiously.

During a routine inspection of the cell, Du Xiangdong found that Xu Wenguo had reoccupied the headboard bed.He immediately found the prison chief Zheng Sanchuang to ask why.Zheng Sanchuang revealed that someone threatened Xu Wenguo's mother and sister's lives and asked him to take good care of Xu Wenguo in the detention center.However, when Du Xiangdong asked the commander behind the scenes, Zheng Sanchuang suddenly collapsed and cried, and no longer disclosed any information.

At the same time, Du Xiangdong privately discussed the case with Zhang Xiangdong, who believed that Xu Wenguo and Yao Binbin had nothing to do with the murder case.But Zhang Xiangdong thought Du Xiangdong was too sensitive and joked that he was more suitable for discipline.

After nightfall, Zheng Sanchuang approached Xu Wenguo and praised his gun-making ability.When Xu Wenguo heard someone asking Zheng Sanchuang to take care of him, he suddenly grabbed Zheng Sanchuang's wrist and fiercely questioned the other party's identity.Zheng Sanchuang was so scared that he broke free and fled to the other end of the cell.

On the other hand, in order to help his children go to school, Du Xiangdong had to ask Zhang Xiangdong for help.At the class reunion, Zhang Xiangdong readily agreed to Du Xiangdong's request.However, after the party, Du Xiangdong sat alone at the table to eat noodles, and did not leave in a hurry until Liu Fenfang took the initiative to talk.

The next morning, the truck from the meat plant was parked in front of the detention center.Liu Fenfang sent a basket of pig's trotters to Du Xiangdong in the name of his family.Du Xiangdong came to the Sixth Machinery Factory to investigate the case and learned from employee Chen Su'e that although Yao Binbin fired a gun, he did not die.At this time, the security section chief Liu Guangcai appeared. Du Xiangdong accidentally dropped his workbook while escaping through the window, but was caught and threatened by Liu Guangcai.