Chapter 643: The Inescapable Problem

The next day, Wang Mengqi was summoned to the station for questioning. Chen Shi and Lin Dongxue were in charge of the interrogation. Chen Shi began, “Mr. Wang, we meet again.”

“Get to the point. I have work to do,” Wang Mengqi replied impatiently.

Chen Shi opened a laptop and played a video. It was surveillance footage from a supermarket opposite Wang Mengqi’s company. Wang Mengqi’s eyebrows twitched slightly as he saw himself leaving the company at 4 PM on November 19th.

“You claimed to be on a call with Geng Qing using the office phone as your alibi for that day. However, this footage shows you leaving at 4 PM. Where did you go?” Chen Shi asked.

He then played another video, this one from outside a park, and paused it, pointing to a person in black entering the park. “I asked if you owned this outfit, remember?”

“I answered that it’s a common outfit. Many people have one. This doesn’t count as evidence,” Wang Mengqi retorted.

“But we found your ride-hailing record for that afternoon, and the destination was the park. How do you explain that?” Chen Shi pressed.

Wang Mengqi bit his lip, his brows furrowing deeply.

“Are you thinking you made a mistake?” Chen Shi asked pointedly.

“Just because I called for a ride doesn’t mean I took it,” Wang Mengqi tried to argue.

“Nice try, just like when former U.S. President Clinton said that finding semen on a secretary’s dress didn’t mean they had a relationship. Should we bring in the driver to identify you?” Chen Shi countered.

“I have a busy job. Sometimes I have to cancel plans because of a call from my superior. So even if I called for a ride, I might not have taken it,” Wang Mengqi explained, sweating profusely.

“We’ll verify that. As for your alibi, I believe you faked it. You started the call with Geng Qing at 4 PM using the office phone, but you taped a mobile phone to the receiver to use the landline remotely. I was suspicious when you insisted on using the office phone. We checked your office phone records and found you only used it for internal calls, never for outgoing calls. Isn’t that a bit suspicious?” Chen Shi asked.

Wang Mengqi was visibly angry, raising his chin defiantly, “Just say what you mean, no need to beat around the bush.”

“We suspect you killed Geng Changle,” Chen Shi stated.

“Hah! Based on this? The park is open to the public. Anyone could go there. How does that make me the killer? What motive would I have?” Wang Mengqi retorted.

Lin Dongxue handed him a paternity test result. Wang Mengqi’s expression changed drastically upon seeing it. Chen Shi continued, “Geng Changle is your biological father. I think he already told you. He arranged a match between his daughter and Factory Director Wei, asked you for money to send Geng Qing abroad, all to separate you two. Geng Changle had complicated feelings for you. You’re his son, he loved your mother in his youth, and had deep affection for you. But he absolutely couldn’t let you and your sister get married!”

“He loved me?” Wang Mengqi shouted. “That old bastard knew who I was from the start. He always demanded things from me, eventually even money, as if it was his right. He never did anything for me as a father, yet now he tries to ruin my relationship with Geng Qing. One day, he reveals the truth: I’m his son, and Geng Qing is my sister. All his sins from the past are now our burden!”

“So you killed him?” Chen Shi asked.

“No!!!” Wang Mengqi vehemently denied, though his expression betrayed him. “I’ve never killed anyone. I don’t know how Geng Changle died. He was my father, how could I kill him?”

“Geng Changle died from a poison. We discovered that purchasing this poison required 400,000 yuan. You borrowed 400,000 from a loan company, gave it to Geng Changle, and then used the card to buy the poison right before he died, and carried out the murder that afternoon,” Chen Shi explained.

Sweating profusely, Wang Mengqi tried to maintain his composure. He laughed, “These are all your guesses. None of this happened. You say he was poisoned, but what kind of poison? You can’t find out, so it must be sudden death!”

Chen Shi had anticipated this response. The poison was indeed untraceable, even if Wang Mengqi went to court, the evidence might not suffice for a conviction.

The 400,000 yuan was well spent.

Lin Dongxue exchanged a knowing look with Chen Shi. The interrogation had essentially confirmed Wang Mengqi as the suspect, but a major obstacle remained.

“Should we detain him?” Lin Dongxue asked.

“What’s the point? We achieved our goal for today,” Chen Shi replied. “Let’s release him.”

As Wang Mengqi left the interrogation room, his clothes soaked with sweat, Chen Shi told him, “Mr. Wang, you know what you did, and so do we. The evidence will come to light sooner or later.”

Wang Mengqi, his pride wounded, stared Chen Shi in the eye and whispered, “Investigate all you want. No one can stop us from being together!”

After he left, Lin Dongxue said, “We knew he wouldn’t confess easily, but the clues are clearer now. Let’s focus all our efforts on him. I’ll report to Captain Lin.”

“I’ll check with Peng Siyue to see if he has any progress,” Chen Shi replied.

Chen Shi went to the technical team but found out Peng Siyue was in the reading room. He found Peng Siyue there, surrounded by thick books on toxicology, chemistry, and radiology.

Seeing Peng Siyue’s dark circles and pale face, Chen Shi guessed he hadn’t slept all night. He sat next to him and said, “Do you have to push yourself this hard?”

“I think I’ve got it…” Peng Siyue’s voice was hoarse. He pinched his nose and said, “Come with me for a smoke.”

In the hallway, Peng Siyue’s hands trembled as he lit a cigarette. Chen Shi, concerned, lit it for him, saying, “You’ve been researching all night? Do you think you’re still young enough to pull all-nighters?”

Exhaling smoke, Peng Siyue gathered his energy. “I couldn’t sleep without figuring this out. I dozed off in the library and had an epiphany in my dream. The poison might be potassium!”

“Potassium?”

“It’s a radioactive substance but also a trace element essential to the human body. Bananas contain potassium. Excessive potassium can cause arrhythmias and respiratory muscle failure. If it’s a hundred or a thousand times the normal level, it can cause instant cardiac arrest. Both victims had high potassium levels in their blood. At first, I thought of snake venom, which can cause similar symptoms. But several spectral analyses and protein removal tests showed no signs of snake venom. In my dream, I realized the killer used high-concentration potassium. It’s a natural substance in the body, and the killer added interfering substances, so we couldn’t detect it.”

“Brilliant, as expected of a top forensic student. You figured it out. The suspect just left; I’ll go bring him back for formal arrest!” Chen Shi exclaimed.

“It’s useless,” Peng Siyue shook his head wearily. “This is still a hypothesis, albeit one close to the truth. We can’t prove how the potassium entered the victims’ bodies without a sample of the poison to establish a link between the suspect and the poison seller.”

“So, we still need to catch Xu Fa?” Chen Shi said. The truth was so close, yet so frustratingly out of reach.