Animal Detective

Old Lv’s full name was Lv Yajun.

By the time Shen Xin and his partner arrived, he had already finished work and left for the day.

But after a quick phone call, he immediately turned around and came back.

"Fipronil?"

Lv Yajun was a man in his fifties who wore glasses. After hearing the details of the case, his brow furrowed immediately.

He gestured for the two of them to sit.

He was very familiar with Fu Lanting’s poisoning case; he had been the one in charge of the toxicology tests back then.

He also knew that Shen Xin’s team had reopened the investigation. Ding Yuwei and the others had come to ask him questions more than once.

But he never expected the investigation would now lead to Guo Jinhua.

After a moment of thought, Lv Yajun said, "It should be possible."

"After fipronil enters the body, it rapidly metabolizes into fipronil sulfone and fipronil sulfoxide. Fipronil sulfone is the key target for detection."

"The chemical structure of this stuff is extremely stable. It’s highly lipophilic, so it should accumulate in the liver’s fatty tissues. Under low-temperature storage—our lab keeps samples at minus eighty degrees Celsius—its degradation would be further slowed."

"So even after two years and eight months, I believe we can still detect it."

"And it’s not just Fu Lanting. We also drew blood from Guo Jinhua back then and kept the sample. We might be able to detect traces of fipronil in his blood as well. That should be helpful, right?"

’Of course it would be,’ Shen Xin thought. ’It would prove they were both poisoned with the same substance.’

Lv Yajun continued, "Fipronil is a phenylpyrazole neurotoxin that affects the central and peripheral nervous systems."

"Given the dosage you mentioned, the symptoms would be milder and would share some overlap with those of bromadiolone poisoning."

"For instance, the initial numbness in the hands and feet, dizziness, and nausea."

"I recall Guo Jinhua suffered severe neurological damage and memory loss. That might have also been due to the effects of fipronil."

At this point, Lv Yajun stopped talking, stood up, and began to put on his white lab coat. "Wait for my report," he said.

He glanced at the wall clock and gave a timeframe: twelve hours.

The detection technique itself wasn’t difficult, but the frozen tissue samples required pre-treatment, which would take more time.

Still, that was fast enough. After all, this was a criminal case, so he’d have to get it done even if it meant working overtime through the night.

Shen Xin thanked him. After leaving, he called Zhang Hancheng to report on the situation.

"Nice work, Shen Xin."

Zhang Hancheng exclaimed in pleasant surprise after hearing the update.

They had just discovered a potential motive, and now, so quickly, they had traced the source of the poison and had a good chance of getting a toxicology report.

Zhang Hancheng had been a criminal investigator for many years, working his way up to captain of the Criminal Investigation Detachment. He had handled countless cases.

But it was rare for one of his cases to go cold.

He remembered every single one that did, and they all weighed on his mind.

Now that there was hope of solving this poisoning case, how could he not be thrilled?

However, Zhang Hancheng knew better than anyone not to celebrate prematurely, especially at a time like this.

After thinking for a moment, he said, "Shen Xin, you need to keep digging in Qiong Province. Specifically, find out exactly who sold that bottle of rat poison to Guo Jinhua."

"Since you’ve already called in a favor, you might as well go all out. Thoroughly investigate Guo Jinhua’s movements in Qiong Province. My personal guess is that he bought it somewhere secluded, probably near his hotel."

"Because these kinds of illegal products, often advertised as some high-tech solution, are usually sold at street stalls."

The kind you see at farmers’ markets or neighborhood entrances—they set up a small stand with all sorts of exaggerated ads. Their main strategy is to strike once and move on to avoid getting caught.

It also saves them from being tracked down by buyers when the fraudulent poison they sold doesn’t work.

"Hasn’t the manufacturer been shut down? Investigate their sales channels. Trace them down, level by level, and then cross-reference that with Guo Jinhua’s movements. If you find a match, go verify it."

"During the airport security check, didn’t he say he paid a lot for it? That means the seller charged a high price, probably thinking they’d just scam one person and be done with it."

"So, the sales volume was probably low. The seller might still remember him."

"In any case, you must find the source of that rat poison. That’s how we can lock down the case against Guo Jinhua."

Shen Xin made a mental note.

On the way over, Shen Xin had already thought about how crucial it was to trace the origin of the rat poison.

In this case, the method and tools used for the poisoning would be difficult to determine now, so their only angle was the poison itself.

Just now, Shen Xin had asked Lv Yajun.

He learned that fipronil, like bromadiolone, could only be broken down by high temperatures.

Back then, extensive samples had been taken from the back kitchen and Guo Jinhua’s home, but no traces of bromadiolone were ever found.

This was actually a major reason why Guo Jinhua wasn’t suspected at the time, and why they could never figure out a plausible poisoning method.

Because if Guo Jinhua had administered the poison, he would have surely cleaned the utensils afterward.

But conventional cleaning methods would have struggled to remove all traces.

Not to mention, he was supposedly poisoning her over a long period.

That’s why the original task force had racked their brains, coming up with all sorts of outlandish poisoning scenarios.

This was a problem Shen Xin had already considered after he began to suspect Guo Jinhua.

It was possible that Guo Jinhua had used disposable utensils.

They ate almost all three of their daily meals at the noodle shop. What if, for convenience, he used disposable takeout containers?

He could add the poison, and once she finished eating, he could just throw the container away somewhere far from the shop. With the long time between the poisoning and the discovery of the crime, the discarded trash would be impossible to find.

Therefore, the only way to pin it on Guo Jinhua was through the rat poison, using the principle of exclusion.

So as long as they could trace the rat poison, they could immediately issue a warrant for Guo Jinhua’s arrest.

As for his motive, that was a question for after the arrest.

Once the source of the rat poison was confirmed, the people he’d called in from Pingyu could be sent back.

They were busy people, after all.

Now, they just had to wait for Yang Zeran to keep working on it and see if he could find the seller.

The next day, Lv Yajun successfully produced the toxicology report.

Traces of fipronil were definitively found in Fu Lanting’s tissue samples.

It was also detected in Guo Jinhua’s blood.

Now, all the pieces were in place; they just needed the final push.

It had to be said, pulling strings made a difference. Their colleagues in Qiong Province put in a lot of effort, and after a few days of tracing leads level by level, they actually found him.

On July 13th, two days before Guo Jinhua and his family left Qiong Province, they went to a seafood market in Yazhou to buy some fresh seafood, planning to have a feast.

A street vendor named Huang Shaolong had set up a stall outside the market, selling rat poison.

He claimed that one diluted bottle would last for three whole years, and that a single drop could kill all the rats and pests in a house.

"Imported high-tech, exclusive secret formula, special grand-opening discount, only 198 yuan a bottle."

The guy was using the same old sales pitch as those knife or cleaning cloth hawkers. He even did a live demonstration, diluting the poison and feeding it to caged rats and cockroaches, which would drop dead within minutes.

The demonstration attracted a large crowd of curious onlookers.

Huang Shaolong remembered Guo Jinhua.

The reason he remembered was that Guo Jinhua’s family of three had also been drawn in and were watching from the crowd.

Then, possibly after seeing the rats convulsing as they died, Guo Meijing, who was herself near death, couldn’t bear it. She begged Huang Shaolong to spare the rats.

She even pleaded with Guo Jinhua to buy all the rats and set them free.

Guo Jinhua actually agreed and tried to negotiate with Huang Shaolong to buy the rats.

Huang Shaolong thought he was a fool and naturally refused to sell.

Fu Lanting chimed in, saying Huang Shaolong was being too cruel and that even a child couldn’t stand to watch.

They ended up getting into an argument over it.

Because of this, Huang Shaolong remembered Guo Jinhua.

But more importantly, after the argument, the family left. About two hours later, just as Huang Shaolong was getting ready to pack up his stall, Guo Jinhua returned alone.

Huang Shaolong thought he had come back to argue, but to his surprise, Guo Jinhua bought a bottle of rat poison from him, asking detailed questions about how to use it and how toxic it was.

Huang Shaolong recalled that Guo Jinhua had even asked what would happen if a person accidentally ingested it.

A seller with a conscience might have become suspicious at such a question.

But not Huang Shaolong. He just casually said it would be best not to eat it.

Huang Shaolong also remembered that Guo Jinhua had acted strangely, even smelling the poison before deciding to buy it.

He didn’t even haggle over the price.

This Huang Shaolong had been reported for selling fraudulent products before and had been busted by the authorities.

Yang Zeran had already shown him photographs to confirm it was indeed Guo Jinhua’s family of three.

With that, the entire chain of events—from the source of the rat poison and its sales channel to how it ended up in Nanjiang—was crystal clear.

Under these circumstances, even if Guo Jinhua denied it to his last breath, there was enough to form a complete chain of evidence confirming that he had poisoned and murdered Fu Lanting.

The only thing that made Shen Xin feel a bit emotional was that Huang Shaolong’s memory of Guo Jinhua was all because of Guo Meijing.

Because of Guo Meijing’s kind heart, she couldn’t bear to see those rats being poisoned.

Looking back at the entire case, it felt like its resolution was all tied to Guo Meijing’s kindness.

The reason He Liyuan still remembered Guo Meijing was because she was such a good child, and the wish she had made had stuck with her all this time.