As night fell and the sound of the clapper at midnight faded into the distance, the dim light in this temporary dwelling, converted from a dilapidated temple, stubbornly shone on.

Shen Jintang sat at the desk with her hair down, her expression focused and resolute.

Xinghui and Liuhuo brought over wooden buckets, fine linen, and dried wood ash as instructed.

The wooden barrels were a bit old, but supplies were scarce in the western quarantine zone, and after searching for a long time, these were the only ones they could still make do with.

Shen Jintang didn't say much, but simply followed the drawn blueprints to arrange the wooden barrel.

“Master, why don’t you go and rest for a while?” Xinghui said, her voice full of worry as she watched Shen Jintang carefully drill small holes in the bottom of the wooden tub. “Your fever has just subsided…”

Shen Jintang simply smiled slightly, her voice soft yet undeniably firm: "The plague is most averse to filth. If the water we drink is not clean, the plague will continue for a longer period of time."

She carefully laid the fine linen cloth flat on the bottom of the bucket, dipped her fingertips in charcoal ash, and drew clear markings on the bucket wall, explaining them to Xinghui and Liuhuo.

"A layer of ash filters out toxins, a layer of sand removes impurities."

Her voice was soft, carrying a hint of weakness from recovering from a serious illness, yet it sounded exceptionally clear in the quiet night.

Liu Huo immediately took over these strenuous tasks.

"Lay more on."

Shen Jintang's hoarse voice, mixed with the sound of planing wood, echoed in the dilapidated temple.

Fine beads of sweat glistened on Liu Huo's forehead as he carefully laid the seventh layer of straw inside the wooden tub. Though his movements were swift, he dared not be careless in the slightest.

Wood chips danced in the air, landing on his hair, but no one paid any attention.

Xinghui knelt on the straw mat, tearing the fine linen into neat squares. With each fold, she would steal glances at Shen Jintang's expression, afraid that she would fall ill again.

Her eyes were full of heartache, but she dared not say anything.

Moonlight slanted in through the drafty window, casting a soft glow on Shen Jintang's pale face.

Shen Jintang was layering dried mugwort ash and fine sand into a bucket. His well-defined fingers were covered in black ash, but his wrists still bore the bruises from when he was making the filter.

The bruises were particularly glaring in the moonlight, but she seemed oblivious, focusing intently on completing her work.

"Master..." Xinghui handed over a damp handkerchief, her voice trembling slightly, "Why don't you rest for a while?"

Shen Jintang took the handkerchief and gently wiped the dust off her hands, but shook her head, her eyes still fixed on Liu Huo as he forcefully pressed the sand layer down.

Her thoughts drifted far away at that moment, and she vaguely recalled that when she was twelve years old, her father took her to make the same filter in the military camp in the northern border region.

Amidst the swirling snowflakes, the general stroked her head and said earnestly, "Remember, clean water keeps people alive."

The flickering lights illuminated Shen Jintang's slightly sickly face, her gaze gradually blurring, yet her resolve only grew stronger.

She wanted to do everything in her power to save these people, as much as she could.

By the time dawn broke the next day, Shen Jintang and the others had barely finished making the filter.

She leaned wearily against the desk, slightly out of breath, but a hint of relief shone in her eyes.

"The flowing fire will gather everyone at the well."

Shen Jintang gave the order, his voice tinged with weariness, yet still clear and strong.

"yes."

Liu Huo immediately turned and left, his steps hurried.

Before the morning mist had even dissipated, the people of the west side of the city were summoned to the well.

They rubbed their sleepy eyes, gathered in twos and threes, and talked in hushed tones.

"Why did Lord Siyan summon us so early in the morning?" a woman with a headscarf asked in a low voice, her eyes filled with doubt.

The old man next to him rubbed his hands together, breathed on them to warm them, and said in a low voice, "Who knows? I heard that the light in the adults' room was on all night last night."

"Could it be that we're going to conscript labor again?" A young man looked around warily, his voice lowered, and a hint of unease in his eyes.

The murmurs among the crowd grew louder, and many people wore expressions of confusion and unease.

Until Liu Huo shouted loudly, "Silence! Lord Si Yan has something to say!"

The murmurs gradually subsided.

Shen Jintang walked slowly to the well platform. Her face was still a little pale, and there were faint dark circles under her eyes, but her eyes were exceptionally clear.

She raised her hand slightly and whispered, "Xinghui, bring the things up."

Xinghui and Liuhuo worked together to lift a strange wooden barrel and place it in front of everyone.

There was a small hole drilled in the bottom of the wooden barrel, and it seemed that something was lined inside.

The people looked at each other in bewilderment, and murmurs arose again.

"What is this?" A child tilted his head curiously, his eyes full of doubt.

"It looks like a bucket, but why is there a hole in the bottom?" a woman muttered to herself.

"Are you suggesting we use this to fetch water? But how can this hold all the water?" An old man frowned, his face full of confusion.

Shen Jintang did not explain immediately, but instead picked up a pottery jar and drew a bucket of turbid well water from the well.

Under the watchful eyes of everyone, she slowly poured the sewage into the strange wooden bucket.

The sewage flowed through the wood ash, creating fine foam. After passing through the gravel layer, it gradually became clear. Eventually, the water seeped out from the small hole at the bottom of the bucket and dripped into the earthenware jar below.

Surprisingly, the water that flowed out became crystal clear!

A gasp of surprise erupted from the crowd.

"The water has become clean!" A woman covered her mouth in surprise, her eyes filled with disbelief.

"My God, is this some kind of magic?" An old man stared wide-eyed, his face filled with shock.

Shen Jintang held up the filtered water, her voice calm yet firm: "This is not magic, just the simplest filtration. Dirty water passes through wood ash and fine sand, which removes most of the filth."

She paused, then added, "The reason why the epidemic keeps recurring is largely because people are drinking unclean water."

Her words made everyone suddenly realize the truth.

"So that's it! No wonder we weren't getting better no matter how much medicine we took!" A young man slapped his forehead, his face full of regret.

"Lord Siyan even understands this, it's truly amazing!" A woman exclaimed, her face full of admiration and her eyes brimming with gratitude.

Shen Jintang continued, "From today onwards, every household can use this method to filter drinking water. Xinghui and Liuhuo will teach everyone how to do it."

As soon as she finished speaking, the crowd suddenly burst into cheers.

"Lord Siyan is truly benevolent!"

"Thank you so much for saving my life, sir!"

"Our Lord Yan from the west of the city is truly blessed!"

The cheers grew louder and louder, and some people even knelt down and kowtowed to express their gratitude.

Faced with such a lively scene, Shen Jintang frowned slightly and unconsciously took a half step back.

She wasn't good at dealing with such flattery, but seeing the genuine smiles on the faces of the people, she didn't say much, only nodding slightly.

Xinghui noticed that her master's hand, hanging by his side, clenched slightly and then slowly relaxed.

She knew that her master was always cold on the outside but warm on the inside, and that he always did practical things. It was only right that these people thanked him.