Undercurrents and a Visitor

Three days later, Lu Qinghe returned from town, looking unwell.

He entered the main room, said nothing, and first walked to the window, peeking out through a crack.

Lu Yuan put down his charcoal pencil. "Father?"

Lu Qinghe turned around, rubbing his thumb against the calluses on his index finger. "When I went to the general store today, Old Liu said there were a few unfamiliar faces in town."

The room fell silent. Mo Chen stopped carving, Shen Moxin closed her notebook. Su Yan and Li Wangye, who were training in the backyard, also came in.

"Not like traveling merchants or hunters," Lu Qinghe said in a low voice. "They sat in taverns for half a day, striking up conversations with people. Asking if any out-of-town Soul Master were passing through, or if anyone was seriously injured and looking for a doctor." He paused, "They even specifically asked about poisoning."

Mo Chen snorted coldly. "They're coming for us."

Lu Yuan tapped his index finger lightly on his knee. "How should I ask the question?"

"They're going around in circles, claiming to be searching for relatives. But their questions are far too detailed, abnormally so," Lu Qinghe. "Three of them, dressed in grey cloth, with northern accents."

To the north, in the direction of the Cloud Mist Sect.

Lu Yuan stopped knocking. "Father, don't go these next few days. If you need to replenish supplies, have Su Yan or Wangye go in shifts, and change their clothes. Bai Zhi and her brother cannot show themselves. They will take turns guarding the gate at night."

He looked at the two boys. "Training continues as usual, keep it as quiet as possible. Cover the windows when using your essence."

Su Yan and Li Wangye nodded vigorously.

"Let's wait and see," Lu Yuan concluded. "But have an emergency kit ready, and keep important items separate. Just grab what you need and go if anything happens."

Mo Chen weighed the array plate in his hand. "If they really come knocking, I'll knock a few of their teeth out."

The words were harsh, yet the air tense. Dusk pressed down heavily.

In the evening, there was a knock at the side gate of the backyard.

He tapped very carefully, three times, stopped, then three more times.

Su Yan and Li Wangye exchanged a glance and silently moved into the shadows. Inside the main room, Lu Yuan paused, his pen poised.

Lu Qinghe came out of the kitchen, and Mo Chen slipped out of the side room.

Lu Yuan stood up. "I'll go."

He walked to the door but didn't open it immediately. Through the crack, he saw a thin figure standing outside. The figure wore a faded gray-blue old shirt, carried a tattered bundle, and looked weary and travel-worn.

But those eyes, in the twilight, shone with a clean, stubborn light.

Lu Yuan had an excellent memory. In an instant, a figure flashed through his mind— Notting Junior Academy, the lecture hall, the middle-aged tutor in the back row by the window who was always quietly taking notes. His surname was Wen.

He opened the courtyard gate.

The person outside saw him, paused for a moment, and a mixture of excitement and trepidation flashed in their eyes. "Lu... Lu Yuan, classmate?"

"Mentor Wen," Lu Yuan nodded, "Please come in."

Mentor Wen paused for a moment before stepping over the threshold, clutching his bundle tightly. At the entrance of the main room, Lu Qinghe, Mo Chen, Shen Moxin appeared silently, their gazes all fixed on him.

Mo Chen's eyes were sharp. Shen Moxin adjusted her glasses and calmly scanned the other person's clothes and shoes. Lu Qinghe's body was slightly turned to the side, in a protective stance.

Mentor Wen felt uncomfortable under his gaze and forced a wry smile. "Excuse me for bothering you."

Lu Yuan led him into the house and lit an oil lamp. In the dim light, the weariness on Mentor Wen's face appeared even deeper.

"Sit down." Lu Yuan sat down opposite him. "How did you find this place?"

Mentor Wen placed his bag at his feet, rested his hands on his knees, and sat upright but looked dejected. "I was fired by the college six months ago. The reason was that I didn't fit in, and my teaching was 'off-track'... Also, they insisted on recommending your model."

He paused, then looked at Lu Yuan, "I left Nuoding City and traveled around. A few days ago, in a small town north of the Black Stone Mountain Range, I heard a rumor..."

"They say this area is unsafe; there are sects hunting people down, and also reports of 'strange Soul Master ' appearing." Mentor Wen spoke slowly and clearly. "Three days ago, I overheard two passing Soul Master chatting at a tea stall, mentioning ' Maple Leaf Town,' 'the young man surnamed Lu,' and 'unorthodox practices.'"

His eyes were clear. "Of all the students I've taught, you're the only one with the surname Lu. I remember your thoughts from back then so vividly. You just thought you'd try your luck here."

The main room was silent.

Mo Chen suddenly spoke, his voice cold and hard. "You come knocking on our door based on a few rumors? Aren't you afraid you've come to the wrong place? Aren't you afraid we're bad guys?"

Mentor Wen turned to look at him, his wry smile deepening. "I inquired along the way. The closer we got to Maple Leaf Town, the more fragmented information we found—unfamiliar faces asking about 'out-of-town Soul Master ' or 'injured people seeking medical treatment'; the price of salt at the general store had increased by half a coin; the blacksmith was taking on urgent work, making 'non-reflective, inconspicuous' wristbands."

His gaze swept over the people in the room. "Piecing these fragments together, and considering my understanding of Lu Yuan... I think I haven't made a mistake."

Shen Moxin narrowed her eyes slightly behind her glasses. "You're very perceptive."

"A teacher's flaw is a fondness for observation and association," Mentor Wen, shaking his head self-deprecatingly. "Or perhaps... it's because they're desperate and have no choice but to grasp at any possibility."

He looked at Lu Yuan again, his gaze becoming direct, even desperate. "I meant no harm. Look, I have nothing left. A job, savings, a stable life. All that's left... I'm not resigned to this."

His voice lowered, but every word was clear. "I'm not willing to spend my whole life learning and teaching things just by reciting from the textbook. I'm not willing to have potential ideas buried because they don't conform to the rules. And I'm even more unwilling... to just drift through my life like this."

"So, I came." He raised his head, the stubborn light in his eyes shining brightly under the oil lamp. "If there really is a different path here, no matter how narrow or treacherous, even if it's just for a glance... I want to try it."

The wick of the oil lamp crackled softly.

Mo Chen loosened his grip on the array plate slightly. Shen Moxin seemed lost in thought. Lu Qinghe looked at his son.

Lu Yuan had been listening quietly, his face expressionless. Only now did he slowly speak.

"Mentor Wen," he said, "Do you remember the specifics of my model?"

Mentor Wen paused for a moment, then nodded. "I remember. You used the density gradient and pressure difference of the ' Soul Power particle flow' to explain the Soul Power gathering in the low-level meditation method. You drew a diagram, labeling the key variables and mathematical relationships."

"Assumptions?"

"Soul Power flows through the meridians, much like the steady-state flow of an incompressible fluid in an elastic tube. You've ignored the differences in attributes and only considered the transmission of 'quantity'," Mentor Wen replied quickly.

Lu Yuan nodded and then asked, "If an additional, periodic, weak disturbance source is introduced, such as some kind of external catalytic energy, and acts on the inner wall of the 'pipe,' which variable do you think will be primarily affected? And how will it affect the rate of Soul Power convergence?"

The questions are more specific and in-depth.

Mentor Wen was stunned. A few seconds later, a scholarly focus suddenly shone in his eyes. He looked around, his gaze settling on the dry branches in the corner of the wall.

"Could I borrow a branch? Or the ground...?"

Lu Yuan gestured for him to proceed.

Mentor Wen immediately got up, picked up a twig, and squatted down beside the muddy ground. He brushed away the loose soil and quickly drew lines with the tip of the twig.

First, he sketched out the simplified model diagram from back then, marking the node variables. His movements were practiced and skillful. Then, next to the lines representing "meridians and channels," he added a small, periodically fluctuating symbol to represent the "disturbance source."

He fell into deep thought, the branch hovering in the air. He muttered technical terms under his breath, his fingers tracing patterns on his knee.

Mo Chen frowned as he looked at the scribbles on the ground. Shen Moxin, however, leaned forward slightly, her eyes shining.

After about half a cup of tea's time, Mentor Wen suddenly started moving. The branch moved quickly, scribbling down a few short equations. As he wrote, he explained, his voice low but clear. "The disturbance source acts on the inner wall, first affecting the local 'pipe' equivalent radius... There's an elastic deformation coefficient here... It's transmitted to the upstream and downstream pressure gradients... Considering the periodicity, a time variable and phase difference need to be introduced... The final impact on the average flow rate might be a gain term with a coefficient?"

He finished writing the last stroke, looked up at Lu Yuan, his eyes uncertain, but more so with the pure focus one has when faced with a difficult problem. "Roughly... like this? The specific coefficients and phase effects need more precise boundary conditions and experimental data to verify. My deduction is very rough."

Lu Yuan walked to his side and looked down at the equation on the ground.

It's indeed crude. The assumptions are too idealistic and ignore the complexity of the interaction between Soul Power and meridians.

But his thinking was clear and his logic was consistent. Most importantly, without Lu Yuan's advanced knowledge base, he took a small step forward by relying on his solid foundation and mathematical skills.

The direction is correct.

Lu Yuan stared at him for a long time. Everyone in the main room was looking at him.

Finally, he raised his head and his gaze fell on Mentor Wen's face, which was a mixture of fatigue, trepidation, and vague expectation.

He nodded slightly.

"The deduction has flaws, but the general direction is feasible," Lu Yuan said calmly. "The specific details can be discussed gradually."

Mentor Wen's eyes widened suddenly. He opened his mouth, but in the end, he just pursed his lips tightly and nodded heavily. He staggered as he stood up, and Lu Qinghe reached out to support him.

The lamplight flickered, casting the indelible lines of calculations on the ground in an alternating light.

Like another tiny, newly lit flame.

Outside the window, the night had completely deepened. In the distance, from the town, a few faint sounds could be heard, which quickly subsided.

A night breeze swept through the alley, carrying a chill.

Inside the old house, a warm glow illuminated several faces with different expressions.

Inside and outside the door, undercurrents and Spark collided at this moment.