Wulei Temple was dangerous.
Now he truly understood why. The moment he stepped through the gates, everything fell into place. Why the emperor himself had written the warning signs. Why every source of fire was confiscated at the entrance. Why the storerooms were packed with alchemical materials that had no business being stored anywhere near each other.
He glanced at the column of smoke still curling up behind the main hall and made a firm decision.
He was never coming back here. Never. Even if they beat him like a dog, he would not set foot in this place again.
What surprised him was that, instead of fear, he felt genuine admiration.
The Daoists were running toward the explosion. Not away from it. Their robes fluttered behind them as they sprinted across the compound, faces full of excitement, as though they had just heard someone announce free wine and roast lamb.
Where had the Duke of Wei found people like this? Most men ran from explosions. These people treated them as invitations.
Hou Junji did not relax until he was back outside the gates and standing safely on the street. He sprinted, running as fast as possible from this dangerous place. Only then did his breathing return to normal.
With Li Jing and Li Shiji nowhere to be found, he found himself in an unusually awkward position. He had spent months away from the capital, and now everyone who might explain what was going on seemed to have vanished.
He began scanning through the emperor's inner circle, one name at a time.
Wei Zheng was out of the question. The emperor had sent him on a major assignment shortly after the New Year, much like Hou Junji's own deployment to Hexi. The Ministry of Revenue had reported that after the destruction of the Eastern Turks, more than a million people, both Han and Hu, had migrated south and submitted themselves to Tang authority. Settling such a population was no small matter. New counties had to be established, prefectural boundaries adjusted, farmland allocated, tax records created, and local administrations assembled from scratch.
At the New Year court assembly, the entire problem had been broken down into a mountain of work and handed directly to Wei Zheng.
As if that were not enough, the emperor had assigned him another task once the resettlement effort was complete. Travel north. Gather the bones still scattered along the frontier. Conduct memorial rites in the emperor's name.
For a moment, Hou Junji found himself picturing those distant northern plains. The broken fortifications. The wind sweeping across abandoned battlefields. The countless dead left behind over generations of warfare.
He quickly pushed the thought away.
The capital's streets were far more pleasant.
As he walked, bits of conversation drifted toward him from nearby tea stalls and market vendors.
"Did you see that smoke earlier? Wulei Temple again!"
"Of course I saw it. The whole city saw it. What are they doing in there?"
"Practicing divine arts, obviously. The Thunder God must be angry about something."
"Angry? Why would the Thunder God be angry at a Daoist temple? They worship him."
"That is the problem, you fool. They stopped letting people inside to offer incense. The gods do not like being ignored."
"Apparently just after New Year there was a Daoist who nearly got struck down. Had to have an imperial physician come out to save him."
"It is because the temple stopped letting people in to pray. That is what has drawn the Thunder God's wrath."
"Old Zhang's nephew works near the temple. He said they have been digging holes and burying things. Big ceramic jars. Then they light something and run."
"Burying jars? What kind of ritual is that?"
"How should I know? I am not a Daoist priest."
"Maybe they are trying to summon something. You know, like those stories about the sorcerers of old."
"Summon what? A demon? A spirit? The ghost of Qin Shihuang?"
"Do not joke about that. Qin Shihuang's ghost would burn this whole city down."
"Qin Shihuang has been dead for eight hundred years. If his ghost wanted to burn Chang'an, he would have done it already."
"You do not know that. Ghosts are patient."
"I heard it was a punishment," an old man at the tea stall interrupted, waving his chopsticks. "The emperor closed the temple to common worshippers. Now the gods are showing their displeasure. First the smoke. Then the thunder. Next will be lightning striking the palace itself."
"Lightning? At the palace? Old man, you have been drinking too much tea."
"I am just saying what I know. My grandfather's cousin once worked in the palace. He told me stories."
"Your grandfather's cousin has been dead for forty years."
"Which proves he knows things we do not!"
"That makes no sense, you old fool!"
"It makes perfect sense! The dead know more than the living!"
"You want to fight, old man?"
"I am just saying what I heard!"
Hou Junji almost laughed. The contrast was remarkable. Inside the walls, imperial engineers, generals, and Daoist researchers were trying to unlock future military technology.
Outside the walls, ordinary people were convinced the Thunder God was punishing a temple for closing its doors to worshippers.
Then one particular detail caught his attention.
Imperial physician.
Hou Junji slowed slightly. A moment later, his eyes lit up.
Of course. If anyone knew what had been happening in Chang'an while he was away, it would be the physicians. Officials talked while receiving treatment. Generals complained while having injuries examined. Ministers shared gossip they should not share. Even the emperor spent a surprising amount of time around doctors these days.
The Imperial Medical Bureau might not officially be part of the government's information network, but it probably heard more secrets than half the ministries combined.
A smile spread across Hou Junji's face.
Finally. A useful lead.
He immediately turned and headed for the Medical Bureau.
A quarter of an hour later, Hou Junji found himself standing inside the Imperial Medical Bureau, staring at a young physician's assistant whose eyes kept darting everywhere except at him.
"Where is Sun Simiao?" he asked.
His voice was calm. The assistant somehow looked even more nervous.
"Do not tell me he is unavailable too."
Since Sun Simiao had accepted a permanent appointment, the Imperial Medical Bureau had changed beyond recognition. Drawing on the medical knowledge revealed by the heavenly screen, the Bureau had been reorganized into separate divisions for medicine and pharmacology. The old hereditary system had gradually been dismantled and replaced with a far more demanding one.
Students now lived under a constant barrage of examinations. Monthly examinations. Quarterly examinations. Annual examinations. Anyone who survived that process became a medical clerk. The more talented among them could continue climbing through the ranks as practitioners and senior physicians. The very best eventually earned the title of Doctor of Medicine. The Bureau Chancellor handled the daily administration, but everyone knew who the real authority was. Grand Director Sun Simiao.
"The Grand Director is technically on the premises, Your Grace," the assistant said nervously.
Hou Junji narrowed his eyes. "Technically?"
The young man immediately regretted his choice of words. "He is here," he corrected himself in a hurry. "But he is currently performing a highly sensitive procedure and has forbidden all visitors."
Something inside Hou Junji finally snapped.
Not because of the clerk. The clerk was merely unfortunate enough to be standing in front of him at the wrong moment. Since returning to Chang'an, he had spent the entire day chasing shadows. Fang Xuanling was nowhere to be found. Li Jing was nowhere to be found. Li Shiji was nowhere to be found. Wulei Temple had nearly blown itself into the heavens. And now even Sun Simiao was apparently hiding from him.
Enough.
Hou Junji flicked his eyes toward his retainers. The soldiers understood immediately. They stepped forward and gently but firmly moved the protesting assistant aside.
"Your Grace!"
"I am looking for a physician," Hou Junji replied. "Not attacking a city."
Then he kept walking. His boots echoed through the corridor.
The commotion quickly attracted attention. A senior Doctor of Medicine emerged from a side passage and nearly walked straight into him. One glance at Hou Junji was enough for recognition. One glance at the panicking assistant behind him was enough to explain the situation. The physician felt a headache arriving with remarkable speed.
"Your Grace, please wait." The doctor raised both hands in surrender. "The Grand Director is currently conducting a procedure. Interruptions are strictly forbidden."
Hou Junji stopped. Mostly because the doctor was being polite. That earned him a little patience. "Then announce me."
The physician hesitated.
Hou Junji's expression did not improve. "Tell him that whatever he is doing, I am seeing him today."
The doctor studied his face for a moment and wisely decided this was not an argument worth pursuing. "I understand."
As the physician hurried away, Hou Junji folded his arms and waited. His mood remained foul. Ever since returning from Hexi, he had felt increasingly disconnected from the capital. Everyone seemed busy. Everyone seemed informed. Everyone appeared to know exactly what was happening. Everyone except him.
Even Xuanzang's farewell words had started sounding suspicious in retrospect. Take good care of yourself. Learn to manage your own nature. At the time, Hou Junji had dismissed it as standard monk nonsense. Now he was beginning to wonder.
A few moments later, the physician returned. To Hou Junji's surprise, the man's expression had changed completely. The anxiety was gone. In its place was unmistakable relief.
"The Grand Director will see you now, Your Grace."
Hou Junji raised an eyebrow. "So he finally remembers old friends?"
The physician gave an awkward cough. "The Grand Director specifically mentioned that your particular talents may be useful."
That was not reassuring. In fact, it somehow made things worse. Hou Junji suddenly had the feeling that he had just volunteered for something without realizing it.
Still, retreating now would be ridiculous. He was Hou Junji. Veteran of countless campaigns. Duke of Liguo. One of the founding generals of the Tang. What could Sun Simiao possibly be doing that required his talents?
The physician clearly had no intention of answering. Instead, he pointed toward the rear isolation wing. "The last room."
Then he remained exactly where he was.
That detail did not escape Hou Junji's notice. "You are not coming?"
The physician shook his head immediately. "Absolutely not."
The answer came out so quickly that it somehow made the situation even more suspicious.
Hou Junji stared at him. The physician stared back. Neither moved.
Eventually, Hou Junji snorted and continued down the hallway.
The isolation wing was strangely quiet. No attendants. No patients. No conversations. The deeper he went, the stronger the smell of medicinal herbs became.
At the very end of the corridor stood a heavy oak door. For some reason, Hou Junji found himself remembering the entrance to Wulei Temple.
That was probably not a good sign.
The room was deliberately dim, with the shutters closed to keep out the summer heat. Brass oil lamps burned along the walls, their light flickering across shelves of instruments and casting long shadows over the stone floor.
Hou Junji spotted Sun Simiao immediately.
The old physician stood beside a large wooden table at the center of the room. His white robes were hidden beneath a thick leather apron stained with dark crimson marks accumulated from countless hours of work.
Curious despite himself, Hou Junji looked toward the table.
Then he stopped.
For a moment, his mind simply failed to process what he was seeing.
A human body lay stretched across the tabletop. The chest and abdomen had been opened completely. Metal brackets held the cavity apart, exposing the organs beneath with unsettling clarity. There was no blood-spattered chaos, no battlefield confusion, no violence. Everything was orderly. Careful. Methodical.
And somehow that made it far more disturbing.
Sun Simiao did not even raise his head. Without looking away from his work, he extended a gloved hand toward a nearby shelf.
"There is a scalpel on your left. The blade is about half a finger wide. Hand it to me."
Hou Junji swallowed. His stomach tightened.
He had stood at Xuanwu Gate. He had watched men die by the hundreds. He had crossed battlefields so thick with corpses that the horses had struggled to find clean ground beneath their hooves. None of those memories bothered him.
This did.
On a battlefield, death arrived in a storm of noise and confusion. Men swung swords. Horses screamed. Drums thundered. This room was silent. The only sounds were the crackling lamps and the faint scrape of steel against flesh.
"Master Sun," Hou Junji said at last, his voice sounding strangely strained even to his own ears, "what exactly are you doing?"
Sun Simiao let out a tired sigh. It was the sigh of a man who had spent weeks answering the same question from different officials.
"The emperor personally authorized this research."
Hou Junji stared. That was not remotely an explanation.
Apparently sensing the objection before it arrived, Sun Simiao continued while carefully examining a section of tissue.
"Wang Mang permitted dissection. The Song dynasty permits it. Later generations conduct it as a matter of routine." His tone remained calm and matter-of-fact. "If they can do it, why should the Tang refuse?"
Hou Junji opened his mouth, but no words came out.
Sun Simiao finally glanced over his shoulder.
"If Your Grace intends to help, then hand me the scalpel. If not, kindly stand somewhere else. You are blocking the light."
There was no hostility in the statement. That somehow made it worse.
A few moments later, Hou Junji found himself outside without being entirely certain how he had gotten there.
He remained in the Medical Bureau for the rest of the afternoon. Partly because he still wanted answers. Partly because after seeing what he had just seen, leaving immediately felt like admitting defeat.
So he paced.
And paced.
And continued pacing.
By the time evening arrived, several young medical clerks had quietly begun tracking his route around the courtyard out of sheer curiosity.
When Sun Simiao finally emerged, freshly washed and dressed in clean robes, Hou Junji intercepted him before he could escape.
The physician spoke first.
"It was an unclaimed prisoner from the Ministry of Justice."
Hou Junji blinked.
"The man died from a pulmonary illness. I needed to confirm the condition of the lungs."
Only then did some of the tension leave his shoulders. At least nobody had dragged some innocent citizen onto the table.
Sun Simiao observed the reaction with interest. A faint smile touched the corners of his mouth.
"Does the Duke of Liguo consider my methods excessively bold?"
Hou Junji nodded immediately. There was no point pretending otherwise.
"Of course I do."
The physician chuckled softly. The sound carried more fatigue than amusement.
"Interesting."
Hou Junji frowned. "What is interesting?"
Sun Simiao adjusted his sleeves. "Because from everything I have observed, Your Grace is a far bolder man than I am."
The general looked genuinely confused. "What is that supposed to mean?"
For a few moments, Sun Simiao simply studied him. Then he shook his head. The movement made him look older than Hou Junji remembered. Older and considerably more tired.
"If you are trying to understand why the atmosphere in Chang'an feels different, you are searching in the wrong place. The answers you want are not in the Medical Bureau. They are with His Majesty."
He turned to leave. After a few steps, he paused and added without looking back:
"And before you ask, no, I am not explaining further. I have spent the entire day arguing with officials and examining diseased lungs. I am exhausted."
With that, he departed.
Hou Junji left the Medical Bureau carrying exactly the same problem he had arrived with. The only difference was that now he also knew the empire's most famous physician spent his evenings opening corpses and discussing it as casually as someone commenting on the weather.
Watching the general disappear through the gates, Sun Simiao shook his head.
This was one of the many reasons he disliked the capital. To dissect a single deceased criminal in pursuit of medical knowledge, he had been forced to spend months arguing with ministers, scholars, censors, and moralists. His research had survived only because Li Shimin had personally backed it with imperial authority.
Yet many of those same men would discuss military campaigns over dinner without the slightest hesitation. They recoiled at the sight of one dead body laid respectfully upon a table, but thought nothing of sending tens of thousands of living men into battle so their names might occupy an extra line in the histories.
The contradiction had never made much sense to him. After years of dealing with officials, Sun Simiao had concluded that it probably never would.
Hou Junji's frustration lasted exactly one night.
The following morning, an imperial messenger arrived bearing a summons from the palace. His Majesty requested the Duke of Liguo's presence at a demonstration in the northern district of Chang'an.
As the carriage rolled through the city streets, Hou Junji finally stopped trying to force an answer out of a problem that refused to yield one. After twenty years serving under Li Shimin, he understood a simple truth better than most men. Personal feelings were not particularly important when dealing with the emperor. What mattered was what the emperor thought, and more importantly, why he thought it.
The trouble was that Hou Junji could not identify where things had gone wrong.
When he left for Hexi in the first month, everything had been normal. Li Shimin's attitude had been the same as always. There had been no hidden displeasure, no unusual coldness, no sign that anything was amiss. If something had changed, then it must have happened while he was away.
He considered the possibilities one by one.
The court seemed unlikely. If officials had launched accusations against him through the censorate or stirred up trouble in the capital, the matter would have become public almost immediately. Bureaucrats enjoyed nothing more than making sure everyone knew when they were attacking somebody.
That left only the light screen.
Unfortunately, that answer was even less useful. Hou Junji could predict enemy generals. He could anticipate political schemes. He could plan a military campaign six months in advance and account for contingencies that had not even happened yet. Predicting what people over a thousand years in the future might say about him was another matter entirely.
After several more minutes of fruitless speculation, he gave up and looked out the window instead.
The northern district had been heavily secured. Imperial guards controlled the roads leading into the area, and the open ground beyond had been arranged into something resembling a military testing field. Even from a distance, Hou Junji could see the familiar figures gathered near the center.
Li Shimin stood atop a raised platform overlooking the grounds. Beside him stood Li Jing, who looked thoroughly pleased with himself, Li Ji, who looked exactly the same as he always did, and Yan Lide, whose expression suggested he had recently encountered a problem he would rather not think about.
Hou Junji climbed down from the carriage and approached.
Li Shimin noticed him almost immediately. His gaze lingered on Hou Junji's face for a moment before he gave a faint snort. Apparently, the emperor had correctly identified the look of a man who had spent half the night worrying himself into exhaustion.
Without commenting further, Li Shimin turned back to Li Jing.
"So the gunpowder project finally produced results?"
Li Jing nodded. "We have made progress."
The answer was delivered with enough confidence that everyone present immediately understood the understatement involved.
"We began with every historical reference available to us. The descriptions of saltpeter in the Fanzi Jiran served as a starting point, and from there we systematically examined Daoist alchemical formulas. The practitioner Songcheng proved particularly gifted in this area. Yesterday's formulation generated substantial concussive force and produced a smoke column that closely matched the descriptions preserved by the later generations."
Li Shimin nodded slowly. The glimpses shown by the light screen had taught him one thing. Truly exceptional technical talent was rare. It did not matter whether the field was governance, warfare, engineering, or alchemy. When such people appeared, they needed to be recognized.
"And Songcheng himself?"
Li Jing's expression shifted slightly. "The practitioners are responsible for the formulations. Ignition is handled by trained personnel. Yesterday the guardsman assigned to light the charge permanently lost hearing in one ear."
Li Shimin fell silent for a moment. Then he said, "Reward both of them. The injured soldier will receive a lifetime pension from the treasury. As for Songcheng, grant him an estate outside the city, provide whatever funding he reasonably requires, and ensure he remains under appropriate supervision."
Li Jing bowed his head. Nobody found the arrangement strange. A talented man was valuable. A talented man who routinely created explosions large enough to deafen soldiers was valuable enough to warrant careful observation.
Soon afterward, the demonstration began.
Several soldiers from Wulei Temple entered the testing ground carrying a large ceramic vessel that required multiple men to handle. They marched to a position several hundred paces from the viewing platform and began digging a pit. Once the vessel had been lowered into the ground, the soldiers carefully covered it with earth and ran a long fuse back toward their position.
Li Shimin watched with visible interest.
One of the soldiers stepped forward carrying a torch, lit the fuse, and immediately retreated with the speed of a man who had learned valuable lessons from previous demonstrations. The burning spark raced along the fuse toward the buried charge.
For a brief moment, nothing happened.
Then the earth exploded.
The blast originated underground, which muted the sound slightly, but the effect remained astonishing. Soil erupted skyward in every direction. Dirt and debris rained across the testing field. When the dust finally began to settle, a substantial crater occupied the spot where the vessel had been buried.
The horse tethered nearby for testing purposes no longer resembled a horse in any meaningful sense.
A heavy silence settled over the viewing platform.
Yan Lide stared at the crater with an expression that suggested months of armor design work had just become significantly less satisfying. He had spent a great deal of time improving heavy cavalry and infantry equipment, but looking at the result below, he was beginning to suspect that some battlefield problems could not be solved by adding more armor.
Li Jing remained silent. Li Ji remained silent. Even Hou Junji found himself momentarily at a loss for words.
Li Shimin continued studying the crater. His thoughts drifted back to the scenes displayed by the light screen. He remembered the terrible scale of later warfare, the endless explosions, the burning cities, and the machines that climbed beyond the sky itself.
After a long pause, he finally spoke.
"The later generations used this to kill."
His tone was calm and thoughtful.
"They turned it into weapons and carried those weapons onto battlefields."
His gaze remained fixed on the ruined ground.
"But they also used it to reach places no one in our age can imagine. They used it to study the heavens and uncover truths about the world itself."
The breeze carried the last traces of dust across the field.
"The thing itself is neither good nor evil. The difference lies with the person holding it."
Ten years ago, as the Qin Prince, Li Shimin's first instinct would have been obvious. He would have immediately calculated how to use such a weapon against Dou Jiande, Wang Shichong, or any rival standing in his way. Now, however, he found himself asking a different question.
The Tang had already unified the realm. The empire was prosperous, and its people were beginning to enjoy the peace they had fought so hard to obtain. If this power truly belonged to the Tang, then warfare could not be its only purpose.