Chapter 525: The truth behind the thick fog is within reach

Yu Lingye took a sip of tea slowly.

He placed the teacup on the edge of the table and pointed his long finger at Huo Zhaohe.

"Every June, Shangjing City enters its rainy season. All the rainwater is discharged into the Huozhao River through the drainage system, causing the water level of the Huozhao River to rise rapidly in a short period of time, reaching its highest point."

"To prevent flooding, water officials will temporarily raise the levees of the Huozhao River starting in late June."

"After the dam of the Huozhao River was raised, the terrain became higher than the Yujin River, and the water in the Yujin River could no longer flow into the Huozhao River."

"The Yujin River is the moat of the Imperial Palace. Its terrain is lower than the Imperial Palace, so the water won't flow back into the Imperial Palace. However, the Yujin River is higher than other places, so the water in the Yujin River will flow back into the ditches and canals of Shangjing City."

"The large and small ditches are connected to the underground sewer system of Shangjing City, and the water from the Yujin River will also enter the sewage system."

Xie Yingmian understood.

She still has questions.

"The Shangjing drainage system also flows into the Huozhao River. After the Huozhao River dam was raised, the Shangjing drainage system was completely unable to drain water. If the water from the Yujin River flows back in, wouldn't it cause a backflow?"

Yu Lingye said: "No."

"The weather in Shangjing City is very regular."

"June is the month with the heaviest rainfall every year. Before the June rainy season arrives, all the open and underground ditches in Shangjing are cleaned up."

"When the rainy season begins, all the rainwater and sewage from Shangjing will flow into the Huozhao River."

"This also caused the water level of the Huozhao River to reach a dangerous point."

"Because the Huozhao River has a limited channel and the water volume is too high to be drained out in a short period of time, water conservancy officials temporarily raised the embankment and stopped the drainage."

"When the levee was raised, the rainy season in Shangjing had already passed. The water in the Yujin River seemed high, but Shangjing was very large, and after the water was diverted to various parts of Shangjing, there was not much water left, so it would not cause backflow."

"Once the Huozhao River drains its accumulated water into the sea and the water level drops, the temporary dam will be removed. Once the dam is removed, the accumulated water will flow back into the Huozhao River, thus completing the cycle."

Xie Yingmian narrowed his eyes.

Her fingers tapped lightly on the white porcelain lid of the teacup. “So, the Yujin River is the key to the thick fog.”

Yu Lingye: "The Yujin River is a moat, located above Shangjing City and below the Imperial Palace."

Xie Yingmian: "So, the Yujin River only accepts sewage from the imperial palace."

Yu Lingye chuckled: "That's right."

Xie Yingmian asked a crucial question: "When will the dam of Huozhao River be demolished?"

Yu Lingye glanced at Xie Yingmian with appreciation: "Today."

"After the Ghost Festival, the water level of the Huozhao River will drop to the standard level. The water conservancy department will uniformly remove the dam on July 16th."

"After the dam is removed, the sewage collected in all the ditches and canals in Shangjing City for the past half month will all flow into the Huozhao River tonight, and then flow into the ocean from the Huozhao River."

Xie Yingmian has fully understood the entire chain of the crime.

I also understood Yu Lingye's guess.

Xie Yingmian said, "The Yujin River is the city moat. The guards near the moat are on duty day and night. It would be difficult to tamper with the Yujin River without anyone noticing."

"Only people in the palace have the opportunity to discharge large amounts of sewage without anyone noticing."

“So, the person behind the scenes can only be someone in the palace.

Yu Lingye nodded slightly: "Not bad."

"The only person who can do this is someone in the palace, and this person is of high status."

Xie Yingmian held her chin with one hand: "We have already guessed the means and methods of committing the crime, but we still haven't figured out the cause of the thick fog."

"The composition of sewage is pretty much the same, and it's been fermented, so the composition after microbial metabolism is even more complex, making it difficult to extract useful information."

Yu Lingye picked up the teacup quietly, with an unfathomable look on his face: "That's not hard to guess."

Xie Yingmian raised an eyebrow: "Oh? Do you have any ideas?"

Yu Lingye continued to drink tea slowly and leisurely.

He put down the cup only after he finished his tea.

"The levee will not be raised until the end of June. If the murderer wants to carry out his actions, he will wait until the levee is raised."

"Thick fog only appears on the night of the Ghost Festival every year. It may appear earlier or later, but it will always be contained to the day of the Ghost Festival."

"Also, on the day of the Ghost Festival, all places except the Imperial Palace will be covered in thick fog."

"Don't you think the murderer's control over the thick fog is too precise?"

"They were able to so precisely control the appearance of thick fog, and for over twenty years, they left no evidence. What does this mean?"

Xie Yingmian's eyes lit up.

She is confused by the situation.

The murderer did this under the noses of those in power, and did it for more than 20 years.

Not only did the late emperor have no doubts, but the current emperor also had no doubts.

This in itself is problematic!

If the murderer used chemicals to create the thick fog, it would require a large amount of water and chemicals to create such a large-scale fog, which is impossible.

Not to mention that there was not so much sewage to drain in the palace, the murderer would definitely be discovered if he used so many chemicals.

Therefore, the cause of the thick fog must not be medicine.

There is only one answer to why it is so inconspicuous, unnoticeable, and yet can spread all over the city in a short period of time.

"Insect." Xie Yingmian uttered a word softly.

"Or fungi," she added.

Only insects or fungi can multiply in large numbers in a short period of time.

Yu Lingye said, "I think so too."

Xie Yingmian: "The murderer used the principle of exponential growth."

Yu Lingye didn’t know what the principle of exponential growth was.

He put it in a more understandable way: "There was only one lotus leaf in the pond, and it took half a month for the lotus leaf to cover half of the pond."

“But it only takes one day to go from half the pond to the entire pond.”

Xie Yingmian: "That's right. The initial period of silence is to accumulate the base number. Once the base number accumulates enough and approaches the critical point, the growth rate will suddenly soar."

She was in a very excited mood.

The insects or fungi used by the murderer work on the same principle.

The truth is within reach!

Yu Lingye said, "Given the actual situation, I'm more inclined to believe it's a bug, a poisonous insect."

"At first, only a few poisonous insects flowed from the imperial palace into the Yujin River."

"The Yujin River flows into the sewage system of Shangjing City. The poisonous insects reproduce in large numbers in the sewage, just like that lotus leaf. In the first half of the month, the number of reproduction was not large, and they were scattered in the sewage everywhere. No one would investigate, and it would not arouse suspicion."

"On the day of the Ghost Festival, the poisonous insects undergo an explosive transformation."

"The Gu insects released a large amount of thick fog, which erupted and enveloped Shangjing City."

"The murderer borrowed the legend of the Ghost Festival to rationalize the thick fog as the fog of hell, and rationalized the hallucinogenic effect of the thick fog as the night parade of ten thousand ghosts."

"After the Ghost Festival, the poisonous insects will die like mayflies, flowing into the Huozhao River through the sewage and then into the sea."

"From now on, no evidence will be left behind, whether in the Imperial Palace or the Shangjing sewage system."