Late at night, Qin Chuan couldn't sleep, and he wandered in the corridor of the courtyard.Guo Jiaqi and Liu Lin noticed that he was worried about the Qingjiang case, so they came to discuss countermeasures with him.Qin Chuan observed that the investigators in Qingjiang had put a lot of effort into this case that had been pending for eighteen years, but they had different opinions.At the meeting, Qin Chuan did not rush to express his position, but decided to start the investigation again from the crime scene and review all the physical evidence personally.

Early the next morning, Yang Xiong led Qin Chuan and the expert team to Qiu Zhi's country.Lei Xiuping and Cao Zhongshu took over the case again, and they conducted a meticulous investigation of the scene.Cao Yang, Su Chang and others did not dare to be careless at all, for fear of missing any clues.They worked overtime and conducted detailed tests on the evidence collected at the scene.

At the same time, Yang Xiong, Jin Minghai, Gu Wenlong and others were anxiously waiting for the results in the office.They waited for a long time, but still did not see Cao Yang and Su Chang showing up, so they went to the laboratory to visit them in person and sent them hot meals.However, after careful examination by Cao Yang and Su Chang, they did not find valuable DNA information or a second fingerprint.Although Yang Xiong and others were filled with disappointment, they still forced themselves to look cheerful and comforted Cao Yang and Su Chang.

Qin Chuan presided over a case analysis meeting. He concluded that the case was a property embezzlement case and the suspect should be a local.Qin Chuan elaborated on his views and won the approval of Yang Xiong, Gu Wenlong and others.He suggested that the police concentrate on fingerprint collection. Guo Jiaqi and Liu Lin greatly appreciated Qin Chuan's judgment.Subsequently, Qin Chuan arranged for Guo Jiaqi to stay in Qingjiang and be responsible for fingerprint collection, while he took Liu Lin and Cao Yang to Donglin County, Lincheng City to investigate another murder case.

Cao Zhongshu's work has come to an end for the time being, and he is about to return to the provincial capital.Cao Yang came to see him off and accidentally discovered that he was taking medicine and was deeply worried about his health.Cao Zhongshu made excuses to pass by, and told Cao Yang to follow Qin Chuan in handling the case.Early the next morning, Yang Xiong came to see Qinchuan off, specially bringing specialties from his hometown.

Tao Weizhi, captain of the Donglin County Criminal Investigation Detachment in Lincheng City, was waiting for an important piece of physical evidence in Pingcheng after he learned that Qinchuan had come to investigate the Donglin murder case.He called Su Chang and asked about the itinerary of Qin Chuan and others.Qin Chuan expressed his admiration for Tao Weizhi's unremitting search for clues over the past six years, and asked him, Liu Lin, and Su Chang to introduce the Donglin murder case in detail.

This case occurred on April 19, 2010. Three little girls went missing while going to catch tadpoles and did not return home until ten o'clock in the evening.The family members searched separately and finally found their bodies in an abandoned cave dwelling on the mountain.The provincial department attaches great importance to this case and lists it as a key supervision case on the 15th.

Early the next morning, Liu Lin, Su Chang and Lei Xiuping arrived at the crime scene.Zhong Zhiming, deputy director of the Lincheng City Public Security Bureau, has been waiting here for a long time. He transferred six capable personnel from the municipal bureau to assist in the investigation.The Secretary of the Donglin County Party Committee also personally went to the scene to take command and mobilized the entire county police force to investigate the case.

Fang Wen, director of the Donglin County Public Security Bureau, Yan Jun, director of the DNA laboratory of the Lincheng Criminal Investigation Detachment, Yang Wei, captain of the county bureau's criminal investigation brigade, and deputy captain Cheng Shufeng were busy until dawn.They extracted evidence from the scene and performed autopsies on the three girls.It was initially determined that they died of suffocation and had been sexually assaulted before their death.

Yan Jun briefly introduced the test results: there were five beverage bottles at the scene, three of which contained tadpoles, which were tested to belong to the three victims; there were also two Huangshan brand cigarette butts, and the DNA on the cigarette butts was consistent with the residues in the bodies of the three girls.The objects were consistent and the suspect was determined to be the same person.Yang Wei and Cheng Shufeng also reported on the progress of the investigation respectively: the suspect encountered three little girls on the afternoon of April 18, sexually assaulted them, strangled them to death and hid them in an abandoned cave dwelling.

At this time, Tao Weizhi, deputy captain of the County Bureau's Criminal Investigation Detachment, hurried over and eagerly asked Yang Wei for photos of the scene.Yang Wei dealt with him impatiently and then sent him away.However, Tao Weizhi was not reconciled. He expressed doubts to Su Chang that the murderer could be found based on DNA test results alone.Soon after, he received a call from the investigator saying that a suspicious old bachelor had been found, and he rushed over immediately.

After Su Chang returned to her residence, Tao Weizhi hurried over to ask her about the DNA testing situation.Tao Weizhi interrogated the old bachelor all night, but the old bachelor refused to plead guilty.Su Chang suggested a DNA test to prove innocence. Tao Weizhi arranged the test with the consent of the leader, and the results proved that the old bachelor was not the murderer.This experience allowed Tao Weizhi to see the power of DNA testing technology for the first time.

Subsequently, Su Chang conducted multiple rounds of DNA testing on young men with the same blood type in the village, but no suspect was found.Tao Weizhi was unwilling to give up. He traveled around to investigate and had been busy for four years with no results.Until 2014, when he saw the news on TV that archaeological experts had found the descendants of Cao Cao's family through DNA technology, his eyes suddenly lit up.He immediately found Su Chang's business card and called for help overnight.Cao Yang happened to be present and recommended Wang Ran, a classmate of the Yuhe Criminal Investigation Detachment, to him.Tao Weizhi immediately went to Yuhe to ask Wang Ran for help, and finally found a descendant of the Gu family through Wang Ran who matched the suspect's DNA.