On November 24th, Chen Shi and Lin Dongxue went to Wang Mengqi’s workplace. The secretary told them that Manager Wang had gone to attend a funeral that day. Lin Dongxue said, "Okay, we came in vain!"

"No, I deliberately picked today to come..." He said to the secretary, "We want to see where Manager Wang works."

"I'm afraid I have to ask for permission."

"We’re just taking a look. We won't touch anything. Manager Wang is open and aboveboard. I don't think there will be any secrets, right?"

The secretary reluctantly agreed, and took the two to Wang Mengqi's office. She stood at the side to prevent the two from messing around as it would be difficult to explain afterwards.

Lin Dongxue said, "There are still a lot of leads that can be checked. Why are you focusing on Wang Mengqi so persistently?"

"When investigating a case, the real murderer will always appear in front of you inadvertently. Wang Mengqi gave me the feeling that he was very similar to my outline of the suspect."

"Okay, we’ll trust your intuition!" Lin Dongxue smiled bitterly.

Chen Shi pointed to the phone on the desk and asked, "What is this phone’s number?"

The secretary recited a string of numbers. Chen Shi dialed it with his cell phone and it went through. The internal phone could be used to make external calls. Chen Shi asked again, "On the evening of November 19th, was Manager Wang at the company?"

"November 19th?" The secretary recalled. "I can't remember, but Manager Wang is always alone in the office handling documents every afternoon, so I think he should have been here."

Chen Shi nodded. He picked up the phone and noticed that there was a sticky layer on the receiver. He quietly took a sample.

After the "tour", the two went to look for surveillance footage nearby and brought back everything they could find.

Back at the bureau, Chen Shi went directly to Peng Sijue and asked, "Where is that thing?"

"I’ll give it to you!"

Peng Sijue handed him a document with the photo that he had found at Geng Zhangle’s house that day, and a photo of another woman. This was a feature comparison conducted by a face recognition expert at the Physical Evidence Center. Chen Shi covered up the results below and showed it to Lin Dongxue. "Do you think these two are the same person?"

"The woman on the right is fat, so I can’t tell."

"That day, Geng Qing said that the girl in the photo was her mother. I later found the household registration photo of her biological mother. The more I looked at it, the less they looked like the same person, so I asked an expert for help..." Chen Shi took away his hand, and the results below showed that they were not the same person.

Lin Dongxue wasn't too surprised. "Geng Zhangle was very promiscuous when he was young. It isn’t strange that he had other girlfriends."

There was also a document behind this piece of paper. It was also the results of a facial-features’ comparison. Chen Shi showed it to Lin Dongxue. The result above was that the two were the same person. The photo showed a middle-aged woman that they hadn’t seen before. Chen Shi smiled and said, "But I still found the girl in the picture."

"Who is it?"

"Take a guess!"

"Damn it, you’re being all mysterious again!"

"It's Wang Mengqi's biological mother."

Lin Dongxue was shocked for a long time. "No way?!"

"I did some investigation. Wang Mengqi's parents have a 20-year age gap. I went to the neighborhood to check and confirmed that his father isn’t his biological father."

"I seem to have heard something!" Peng Sijue interjected.

"Old Peng, can I bother you again please? Compare this with the DNA of the deceased." Chen Shi took out a strand of hair, which he had just collected from Wang Mengqi's office.

While the test results were yet to come out, Lin Dongxue’s head was full of wild thoughts. It couldn’t be so coincidental and melodramatic, could it? Wang Mengqi and Geng Qing had such a good relationship, and Geng Zhangle was also very satisfied with Wang Mengqi, but he was secretly trying to break up their relationship. Everything seemed to make sense.

"That day, you told me that they had a ‘husband and wife look’. After careful consideration, some of their characteristics are indeed similar. Along with some other signs, I think the truth is about to come out. Wang Mengqi and Geng Qing may be brother and sister." Chen Shi said.

Lin Dongxue couldn’t really accept it. "When I watched TV series in the past, I thought that this kind of ridiculous plot couldn't happen in reality. There are so many people in the world, how could a pair of brother and sister meet so coincidentally?"

"This is called genetic sexual attraction. Brothers and sisters who grow up together will gradually lose their sexual attraction towards one another. Therefore, the child brides in rural areas in the past often had unhappy marriages with their husbands when they grew up. It’s because they grew up together and were too familiar with each other. However, if it’s a sibling who has been separated since childhood, they will be attracted to each other because of their similar genes. This kind of example is not uncommon."

"You’re quite confident!" Peng Sijue poured cold water on his reasoning. "The result came out. It's not a parent-child relationship."

Chen Shi was confident about his reasoning. He said, "Are you happy lying to me?"

Lying in front of Chen Shi was a waste of effort. Peng Sijue smiled and said, "I just wanted to see your expression when you lost. They are indeed father and son."

"Look, the case is solved!" Chen Shi said.

"This is the motive for the murder? Geng Zhangle knew that Wang Mengqi was his son, so he had been obstructing their relationship. But wouldn't Wang Mengqi in killing Geng Zhangle be killing his father?"

"From his point of view, Geng Zhangle, who is his biological father, is just a stranger. He and Geng Qing were deeply attached to each other. Suddenly, his future father-in-law quietly told him one day that they couldn’t be together because they were brother and sister. This was a big blow to Wang Mengqi. After thinking over it many times, if he couldn’t solve the problem, he would get rid of the person who caused the problem. As long as Geng Zhangle was dead, no one would hinder them. Even if a normal couple has been together for decades, they wouldn’t suddenly go nuts and do a paternity test... I checked. Wang Mengqi's biological mother passed away a few years ago, and as long as Geng Zhangle dies, this secret would be buried forever."

"How irrational. They can go abroad!" Peng Sijue said.

"That's your opinion as an outsider. For the parties involved, this solution will inevitably affect many factors. The most direct issue is whether Geng Qing can accept it or not. Murder is a kind of ultimate solution. This sentence can explain most murder motives."

"So should we summon Wang Mengqi right now?" Lin Dongxue suggested.

"No, let’s do our homework again! We need to be well prepared."

"In fact, I still hold a glimmer of hope in my heart that this is just his secret, and not the motive for the murder... An elder brother killed his father in order to be with his younger sister. It’s hard to accept, even when just thinking about it."

The whole case still lacked a piece of the jigsaw puzzle: the origin of the 400,000 yuan. After checking Wang Mengqi's account, he hadn’t spent 400,000 yuan recently, but he had an inconspicuous expenditure of 3,000 yuan. The other party was a loan company.

The two later found the company. The company refused to disclose the borrower's information. Chen Shi copied their interest rate table and roughly calculated it himself. He found that if he borrowed 400,000 yuan, the monthly interest would be exactly 3,000.

Although Wang Mengqi had a lot of savings, he chose to borrow money from a loan company, hand the cash to Geng Zhangle, and then pay for the poison using Geng Zhangle’s card. This meticulousness was to be praised. If Chen Shi hadn’t caught him, the police might not have found out this inconspicuous lead.

This case almost became an ordinary accident, but it was accidentally solved by Chen Shi. Now, it was time for the truth to come to light...