Episode Summary
The investigation into the fiery car explosion intensifies. Xu Tongsheng's expertise reveals a third person was involved, using an accelerant to ignite the vehicle. Shen Ye discovers a key witness through a video blogger. The autopsy shows the victim was murdered before the fire. Xu Tongsheng and Jin Chun, piecing together a broken cocktail glass, trace it to a bar and a bartender, Chen Xue. Chen Xue eventually confesses to setting the fire after a confrontation with Han Pei, who had previously assaulted her, revealing a complex web of revenge and mistaken identity. Zhao Zhiyuan finally allows Xu Tongsheng to officially join the case.
Spoiler Alert
At the Beixun City Fire Department's fire investigation unit, Mao Mao and Jiang Li are struggling to extract fingerprints from the charred remains of a car involved in a fiery explosion. Seeing Xu Tongsheng also working late, Mao Mao, full of admiration for his skills, asks for his help. Xu Tongsheng readily agrees, joining Mao Mao in the lab and sharing the evidence Mao Mao collected from the scene.
Meanwhile, Shen Ye is meticulously reviewing highway surveillance footage. He notices that Han Pei's vehicle noticeably slowed down inside a tunnel, suggesting a possible driver swap with his passenger, Han Jun. However, the evidence is inconclusive, and the car's dashcam is severely damaged, yielding only partial audio recordings. Despite the poor quality, Shen Ye discerns a female voice in the fragmented conversations.
Xu Tongsheng uses his computer expertise to reconstruct the vehicle's explosion, revealing that, in addition to the two individuals in the front seats, a third person in the back seat triggered the explosion using the brakes and an accelerant. He then visits the forensic department to inquire about the autopsy results. Jin Chun, the medical examiner, mentions that Director Zhao has forbidden Xu Tongsheng from participating in the investigation. She probes whether it's related to an old case involving Xu's family. As they talk, Shen Ye arrives, bringing Jin Chun her favorite: spicy noodles.
The autopsy report confirms Jin Chun's findings: the victim's fingerprints don't match Han Pei's, there's no food in the stomach, and the skin shows signs of secondary burns, indicating the victim was already dead before the car fire.
Back at the fire investigation unit, Mao Mao is again seeking Xu Tongsheng's advice, this time on how to confirm the use of an accelerant in the car. Remembering Zhao Zhiyuan's order to stay away from the case, Xu Tongsheng decides to indirectly help Mao Mao uncover the truth by suggesting he reassemble the shattered glass fragments found at the scene.
Shen Ye's search for additional surveillance footage near the highway incident proves fruitless. While taking a break in his car, he stumbles upon a video blogger who frequently dances at a specific location. In the background of one of these videos, Han Pei's car is visible.
Mao Mao works through the night, even dozing off at his desk. Xu Tongsheng, passing by, decides to help complete the glass bottle reconstruction without disturbing him. Just as he begins, Jin Chun arrives, once again questioning why Xu Tongsheng is barred from the investigation. Xu Tongsheng explains that the details of Wei Kang's murder are strikingly similar to his family's old case, and Han Pei's accident during his arrest further convinces him that these events are not mere coincidences.
Knowing she can't stop Xu Tongsheng, Jin Chun joins him in piecing together the glass bottle. Once completed, they discover a word written on the bottle. Mao Mao, who has just woken up, recognizes it as the name of a specially mixed cocktail from a nearby lab-themed bar. The two head to the bar to investigate.
Xu Tongsheng directly asks the bartender about the "beaker cocktail." The bartender points him to a female bartender, Chen Xue, stating that only she can make it. Xu Tongsheng approaches Chen Xue, who informs him that to order the beaker cocktail, he must first try a series of lower-concentration drinks, as per the bar's rules.
As Chen Xue prepares the bar's signature drinks, Shen Ye arrives at the bar for his own investigation and encounters Xu Tongsheng at the counter. They exchange a few words, with Shen Ye guessing that Xu Tongsheng is there for the beaker cocktail, and Xu Tongsheng realizing that Shen Ye has already targeted Chen Xue.
Mao Mao reports Xu Tongsheng's findings to Zhao Zhiyuan, who was already aware of Xu Tongsheng's covert involvement. Since he can't stop him, Zhao Zhiyuan officially allows Xu Tongsheng to participate in the investigation. Chen Xue is brought to the Binxin sub-bureau. Initially, she claims to barely know Han Pei, stating that he ordered the cocktail at the bar and asked her to deliver it to his car. However, Shen Ye reminds her that Han Pei was supposed to be visiting his parents' graves on the day of the incident and wouldn't have been in the mood for drinks. Moreover, Chen Xue's fingerprints were found in the car. Under pressure, Chen Xue reveals the truth.
She explains that Han Pei was a regular at the bar. One time, he ordered the beaker cocktail, and when she delivered it to his room, he assaulted her. Afterward, Han Pei spent 200,000 yuan at the hotel, leading everyone to believe she had willingly consented. When she told her boyfriend, he broke up with her. To force Han Pei to clear her name, she intercepted him with the beaker cocktail. Han Pei insulted her, and only then did she realize that Han Pei's twin brother was in the passenger seat.
Since Han Pei refused to turn himself in, Chen Xue smashed the beaker cocktail, threatening him. Han Pei grabbed her hair, stopped the car, and pulled her out. Chen Xue then lit a lighter and threw it into the back seat.
