Yao Yuling went to Harbin to meet Jia Jinlong. After she came back, she wrote several letters to Jia Jinlong, but Jia Jinlong didn't reply. Yao Yuling was angry and wanted to fall in love with Niu Dali. Jia Jinlong used the excuse that he was busy with business and had no time, and he did not want Wang Xin and Ma Kui to know about their relationship, so he agreed to take Yao Yuling to Harbin to play. Jia Jinlong used his sharp tongue to coax Yao Yuling into a happy circle. I followed him to eat and buy clothes.
Wang Xin and Ma Kui were busy working on the Pine Forest Dismemberment Case when they suddenly received news from the Yuzhou police that a murder had occurred in Yuzhou. The deceased was named Liu Lan, who was only 26 years old. She was injured by a sharp weapon and bled to death. Wang Xin and Ma Kui followed the local police to the scene and found that the murderer's method of committing the crime was the same as that of the mutilation case. Ma Kui saw that the murderer was deliberately provoking them.
After Yao Yuling and Jia Jinlong reconciled, their attitude toward Niu Dali changed drastically. Niu Dali was only thinking about marrying Yao Yuling, but she didn't expect that Yao Yuling only regarded him as a colleague. Niu Dali committed suicide by taking poison because he was overly sad. Thanks to the neighbors who found out and saved him in time, Yao Yuling learned about this and came to show off her cards to Niu Dali.
Wu Changgui, Cai Danian, Lu Hongxing and Wang Yongge came to talk to Yao Yuling and asked her to take responsibility for Niu Dali. Yao Yuling refused to do it. Wu Changgui threatened and intimidated Yao Yuling. Yao Yuling cried in grievance and they all ran away in fear. Yao Yuling bravely came to see Niu Dali and broke up with him in person. Niu Dali knew that the relationship was irreversible, so he no longer forced it.
Niu Dali learned from the pain and decided to resign and start a business. Wu Changgui and Cai Danian tried to persuade him to no avail. That night, it snowed heavily. Niu Dali stood in the yard and looked at Yao Yuling's room dreamingly. Yao Yuling closed the curtains in anger. Niu Dali vowed to marry Yao Yuling when he made a lot of money.
Ma Kui came out and saw Niu Dali sitting in front of Yao Yuling's house in a daze, so he gave him good advice. Early the next morning, Niu Dali packed his luggage and boarded the train going south. Ma Kui and Wang Xin continued to investigate on the train. A thief named Wei Rui accidentally missed it while stealing. He was so frightened that he ran away in panic. Ma Kui wanted to handcuff him. Wei Rui slashed the back of Ma Kui's hand with the blade in his hand. Wang Xin subdued Wu Rui on the spot, Wu Rui bit Wang Xin's hand hard, and the police took Wei Rui away.
Ma Kui and Wang Xin returned to the police team and saw Captain Jiang and others as if they were facing an enemy. Doctors from the Railway Hospital came to the team to disinfect the team. Only then did they learn that Wei Rui had AIDS. They might be infected and would be forced to quarantine. , Ma Kui and Wang Xin were stunned. They were locked in a ward with Wu Rui. Wang Yongge, Cai Xiaonian and Cai Danian and others came to the hospital to see Wang Xin and Ma Kui and advised them not to have psychological pressure.
Ma Yan arrived shortly afterwards, and she was too anxious to do anything. Wang Xin comforted her instead. Ma Kui asked Ma Yan to take good care of Ma Jian, and Ma Yan cried sadly. The more Wang Xin thought about it, the angrier he became. He forced Xiu Rui to tell him how he contracted AIDS, but Xiu Rui refused to answer and threatened to die with them both. Wang Xin was so angry that he wanted to hit Xiu Rui, but Ma Kui hurriedly stopped Wang Xin. The doctor drew blood from Wang Xin and Ma Kui and sent it to Beijing for testing. If they are not infected with the virus, they can be released from isolation and go home.
Ma Kui learned that Wei Rui was an orphan and was bitten by someone before he was infected with AIDS. Ma Kui cared for Wei Rui very much and helped him sew his clothes. Wang Xin was puzzled by Ma Kui's behavior. He was worried about being infected with AIDS. He vented his bitterness in front of Ma Kui.