Being an emperor is not something he can do, so he can only rely on his connections.

The rain continued to patter, hammering against the green tiles of the government office. Zhang Jingwei had just escaped the stifling coldness of the torture chamber and the wailing of the alchemists, and with lingering anger and fatigue, he happened to encounter the hurriedly walking Inspector Yang Zhao in the corridor.

"Sir," Yang Zhao bowed and glanced sharply at Zhang Jingwei's slightly gloomy face, "I heard that you tortured the two alchemists of the Shi family in the torture room?" His tone carried a hint of subtle inquiry, and it was obvious that the news spread quickly.

Zhang Jingwei didn't stop, but nodded slightly, his voice a little hoarse: "Yes, that's what happened. The bone is too hard, we have to find a way to pry it open."

Yang Zhao caught up with him and asked, "Did you get the result?" His words revealed pressure and worry.

"Soon," Zhang Jingwei said with an almost grim certainty. "No matter how tough a bone is, it will eventually give way. They must reveal what they know." He paused, then suddenly remembered something. He turned to look at Yang Zhao, his gaze piercing. "By the way, Inspector Yang, Lord Liu came to Gaoyang in person today. You submitted the diary you co-organized over the past few days. Haven't I reviewed it yet?"

Yang Zhao's expression froze, and he immediately said, "It was my fault for not thinking it through. When the Lord had just arrived and asked about the local peace and the progress of the case, I directly submitted a copy of the diary I had compiled over the past few days. I hope you will forgive me for not reporting it to you first." He was humble, but his eyes were frank.

Zhang Jingwei waved his hand, indicating it was all right, but his brow furrowed. "Inspector Yang, you and I are colleagues, and we're also responsible for sharing Lord Liu's worries. There's no need to be so rigidly formal. I'm just... a little uneasy." He paused, gazing at the rain curtains that formed a line under the eaves, his voice trailing off. "Teacher, you came this time without urging or asking questions, and even the Governor has arrived. The atmosphere... is too calm. Has something major happened in Yunzhou City that's forcing Teacher to be so... cautious?"

Upon hearing this, a trace of struggle and solemnity flashed across Yang Zhao's face. He was silent for a moment, then he sighed deeply and lowered his voice, "Alas... Lord Zhang is very observant. The affairs of Yunzhou cannot be concealed after all. But right now..." He glanced around cautiously, making sure no one was around before taking a half-step closer and speaking in a nearly whisper, "This matter is over. I must return to Yunzhou immediately! This matter is of great importance, and even a small move will affect the entire situation!"

Zhang Jingwei's heart sank suddenly: "What exactly happened? How could it make the teacher..."

Yang Zhao quickly shook his head, his eyes filled with pleading and determination: "Master Zhang! Please forgive me, I really cannot go into details about this matter! It's not that I don't trust you, Master, but... the more people know, the more disadvantageous it will be for Master Liu! Please understand!"

Zhang Jingwei stared at the unmistakable heaviness in Yang Zhao's eyes, instantly realizing the gravity of the situation far exceeded his imagination. For Yang Zhao, Liu Yanzhi's trusted confidant, to be so secretive, even bluntly stating that it was "detrimental to the teacher," a storm in Yunzhou was imminent.

He took a deep breath, forcibly suppressing his surging thoughts and worries. His eyes became sharp and firm again. "Alright! Since too many people knowing would be detrimental to the teacher, I won't ask any more questions. But Inspector Yang, remember this: as soon as the Gaoyang case is concluded, I, Zhang Jingwei, will immediately take the most capable personnel from the Gaoyang County Government and rush to Yunzhou! To relieve the teacher's worries! Now, we must speed up the progress."

Upon hearing this, Yang Zhao's eyes revealed sincere respect and a hint of relief. "Your Excellency has this kind heart. If His Majesty knew, He would be truly pleased! Your humble servant would like to thank you in advance!"

"That was the last bit," Zhang Jingwei patted Yang Zhao's shoulder and turned to walk deeper into the government office. "Let's go see what Fang Yue's drawings are like. That's the key to this case."

"Yes!" Yang Zhao followed closely.

……

The signing room, once the county magistrate's central office, was now completely occupied. Fang Yue had practically commandeered the entire room to concentrate on drawing waterway maps and conceptual drawings of karst caves. The massive desk was covered with yellowed maps of Gaoyang County from various dynasties, topographical sketches of mountains and rivers, and densely packed notes from his personal exploration of the Sangshui River's source. Scrolls and discarded drafts were scattered on the floor. In the corner, a simple wooden rack was even erected, drying several wet-ink blueprints. The air was thick with the distinct scent of ink, paper, and aged maps.

The dignified county magistrate Zhang Jingwei was squeezed so hard that he didn't even have a place to work. As a result, he was like a wandering soul these past two days, and could only shuttle between the duty rooms of the three shifts (the soap shift, the strong shift, and the fast shift) and the six offices (the officials, the households, the rites, the soldiers, the criminal justice, and the workers), handling official business and listening to reports. His embarrassment was filled with helplessness and urgency.

When Zhang Jingwei and Yang Zhao pushed the door open, Fang Yue was hunched over his desk, one hand pressing down on a large piece of rice paper, the other holding a fine wolf-hair brush, concentrating on sketching a sinuous line. His eyes were sunken and bloodshot, his hair a little disheveled, clearly having not rested for days. His half-worn blue shirt was stained with mud and ink.

"Sir! Inspector Yang!" Hearing the noise, Fang Yue suddenly looked up, with a tired but excited look on his face. He quickly put down his pen and saluted.

"No need to be so polite." Zhang Jingwei waved his hand and walked straight to the desk, his eyes fixed on the increasingly complex blueprint that was taking shape. "Is the drawing finished? This is the final step."

Fang Yue pointed to a thick line marked with cinnabar on the blueprint, extending from a hill (a flat-topped mountain) somewhere in the mountains outside the city into the city itself. He spoke rapidly, "Your Excellency, the key part has taken shape! The continuous rain over the past two days is heaven's help! I've sent people to several pre-set points in the city to observe changes in groundwater levels and water flow. If the data matches, it will confirm whether my inference about the underground river waterway is correct! Your Excellency, please look here..." He pointed to a complex network structure marked in the city center on the blueprint, "Based on the observations of the rainwater infiltration rate and flow direction over the past few days, combined with..."

"There's no time to wait for complete confirmation!" Zhang Jingwei interrupted him, his tone firm. "When your map is finally completed, marking all possible entrances and passages, that's when we'll set off!"

Upon hearing this, Fang Yue's excitement faded slightly, and a deep sense of guilt immediately emerged. He took a step back and bowed solemnly, "Forgive me, sir! I boasted that we could complete the map in one day, but I was arrogant and ignorant, and I broke my promise! Exploring the source of the Sangshui River has taken far longer than expected, and the complexity and strangeness of this underground river system is far beyond imagination..."

Zhang Jingwei stepped forward and helped him up. "Fang Yue, there's no need for this! Your journey beyond the Great Wall to explore the source of the Sangshui River is a great achievement! All rivers in Gaoyang County originate from this source; it's the root. Even more remarkable is your ability to unravel this seemingly ordinary 'mystery of the underground river,' combining historical maps with the oral accounts of elders to deduce the earth-shattering truth!" Zhang Jingwei's voice was filled with uncontrollable excitement. "Who could have imagined that Gaoyang County, right here at our feet, was built atop a massive mountain? Nestled beside the mountain and water is just the surface; the secret lies within the mountain's belly! The existence of this cave not only explains the origin of the underground river, but may also hold the key to our quest for the source of the Five Stones Powder, and even the many secrets of the Shi family! You've accomplished a great deed!"

A few days ago, Fang Yue braved the dangers of the Great Wall and ventured deep into the Great Wall, finally confirming the source of the Sangshui River. All rivers within Gaoyang County originate from this source. However, the underground river within the county, its volume and direction, inconsistent with known surface water systems, posed a profound mystery. Undeterred, Fang Yue interviewed the city's elderly residents, gleaning fragments of legends about a "mountain city" and an "underground river" from vague, oral traditions. He then delved into the dusty piles of archival documents in the county government's warehouse, comparing historical maps of Gaoyang County. Finally, a startling truth, long buried, surfaced: Gaoyang County's original site wasn't ordinary flat land, but atop a steep, flat mountain nestled among mountains! Nestled between mountains and water, it was easily defended and difficult to attack. But if the city was built on a mountain, then a vast system of natural caves was highly likely within its depths. The source and channel of the inexplicable underground river that appeared in the city must be hidden in this huge and secret cave network!

This discovery, like a thunderclap, instantly cleared up all doubts.

Fang Yue is now racing against time, attempting to integrate his field survey data, information from historical maps, clues shared by the elderly, and his own understanding of geological structure to create a realistic "map of the mountainside's karst caves and underground rivers." He has spent several sleepless days and nights in the signing room, with a lamp always burning at his desk.

Zhang Jingwei looked at Fang Yue's bloodshot eyes that sparkled with determination, looked at the gradually clearing drawing on the table that seemed to reveal the earth's internal organs, and then looked at the continuous rain outside the window.