Song Xu led Qin Chuan and his team to the scene of the first serial murder - the junction of urban and rural areas.Twenty-eight years have passed and the old house no longer exists, only ruins remain.Later, the group moved to the dormitory of the Power Supply Bureau, where two murders had occurred. Although the building still existed, the residents had long since disappeared.

Qin Chuan keenly discovered that the nine murder cases were all arranged along the main road.He speculated that the murderer was unfamiliar with the terrain of Liangcheng and preferred to commit murder around 10 a.m. and 1 p.m.In addition to the nearby long-distance bus station, Qin Chuan concluded that the murderer might come from the surrounding suburban counties, while Song Xu speculated that Guanhe, 60 kilometers away, was most likely.

Qin Chuan captured the key clue from the victim's statement: the murderer always wore a pair of popular semi-high-heeled leather shoes.Song Xu and Fan Shouliang visited Liangcheng Shoe Factory but found nothing.Although some experts concluded through DNA that the murderer was from Tonghai, the police could not find any clues among the many Tonghai businessmen in Liangcheng.

Qin Chuan firmly believes that the murderer is in or around Liangcheng.He asked Song Xu to lead the way to the place where the final crime occurred. After hearing the news, the victim's mother came over and begged Qin Chuan with tears to avenge her daughter.Qin Chuan was well aware of the difficulty of reopening old cases, as the scene was annihilated and clues were scarce, but he decided to start with the details, sending Su Chang and Cao Yang to review the inspection materials, and invited Tongcheng trace expert Nie Chengyi to help, and Lei Xiuping accompanied him to visit the shoe factory.In addition, he also invited Cao Zhongshu to participate in the grand event.

Although the shoe factory has closed down, Song Xu managed to contact Master Xia.With the help of Lao Xia, they found shoes that matched the shoe prints at the scene.Nie Chengyi analyzed that the murderer would store the shoes after each crime.Lao Xia recalled that a large number of these shoes were sold to Guanhe, so Qin Chuan decided to focus on investigating this area.

Su Chang and Cao Yang worked day and night to test the samples, and Cao Yang successfully expanded the DNA database.Qinchuan convened a task force to deploy investigation tasks.Cao Zhongshu proposed using new technologies to build a fingerprint database to deal with the problem of fingerprints changing over time.Qin Chuan adopted this suggestion.

At the same time, Tang Yixun was investigating three murder cases in Caohe District, Zhucheng City.The three cases were all targeted at young women. The crimes were committed between 7 and 9 pm in remote locations and close to highways. Mobile phones and cash were robbed.The police checked the mobile phone to no avail, so Tang Yixun asked Qin Chuan for help.Qin Chuan suggested careful testing of the items left at the scene and shared similar cases that Cao Yang encountered while studying abroad.After Qin Chuan arranged his work, he immediately returned to the provincial capital.

Qin Chuan visited Wu Yingde and reported to him the progress of the case.Wu Yingde encouraged Qin Chuan and asked him to organize his investigation notes and information.Qin Chuan readily agreed and applied to Director Yuan Zhen to establish a database, and received full support.

Three months later, Su Chang and Cao Yang received good news. They found the DNA of the same man on the victim Lin Ling and at the crime scene.Qinchuan has established databases in Zhucheng and Lingzhou, and assigned Tang Yixun to be fully responsible for the comparison work.With the assistance of Ou Jiaming and others, the police successfully identified Li Li as a suspect and immediately arrested him.