I'm doing engineering in the instance.

Forty minutes.

Xie Chengzhou mentally settled the number, then sat down on the dam, leaning against the side of the template, and glanced at the number on his wrist.

Water level: 5.88 meters. Distance from warning line: 2.12 meters.

He placed his right hand on his knee and bent his index and middle fingers slightly. The tingling sensation was still there, not completely numb, but rather a decreased precision in tactile sensation, as if there was a thin film separating his fingers from the outside world; he could feel the contact, but not the details. He had been ignoring this sensation during construction, but now that he had stopped, it had come to the foreground.

He turned his hand over and glanced at the back of it.

The mucus had dried, leaving a thin, light gray film with slightly cracked edges, like a shell on the skin. He scratched the edge with his left fingernail, and the film peeled off, revealing normal-colored skin underneath, without ulceration or necrosis. However, the sensation in his two fingers had not fully returned.

It does not affect the operation.

He made a mental note of this judgment and then put his hands back on his knees.

Old Zhao sat down next to him, placed the thermos between his legs, and without opening it, simply rested his hand on the rim of the cup to check the temperature. The cup was still warm, but a little weaker than before. He didn't drink from it, just kept his hand there, as if confirming that the warmth was still there.

Li Gong sat opposite them, his back to the dam facing outwards. The ring and little fingers of his left hand repeatedly bent and stretched on his thigh in a steady rhythm, the rhythm of someone who had made this movement a habit—he wasn't deliberately confirming it, he just couldn't stop.

Xie Chengzhou reactivated the sensation in his feet.

0.09 Hz, still there.

But it's weaker than before.

He kept this change in mind but didn't say it aloud. There was no point in saying it, because the change was still within his predictions—he predicted that large individuals would slow down as the infiltrator group retreated, and now it was slowing down; this was just verifying a pre-existing inference, not new information.

He glanced at his wrist: five minutes had passed.

Water level: 5.89 meters.

Rate of increase: 0.002 meters per minute.

It's slower than when grouting was completed.

"What are you calculating?" Engineer Li said.

It's not a question, it's a statement; it's a way of observing what the other person is doing and expressing that observation.

"We're verifying it," Xie Chengzhou said, "by inferring each link in the chain."

Which rings?

"The repair process triggers the retreat of seepage agents," Xie Chengzhou said. "This link is triggered two minutes after grouting begins, and it has been verified. After the seepage agents retreat, the larger ones slow down; this link is still in progress and has not yet been fully verified. After the larger ones slow down, the water pressure transmission slows down, and the rate of rise decreases; this link has data to support it, but the causal relationship needs more data points." He paused for a moment, "After the curing is completed and the cracks are sealed, the seepage agents lose their reason to approach—this link does not yet have data."

Mr. Li bent his ring finger all the way down, paused for a moment, and then straightened it.

"You mean," he said, "that they won't come back after the repairs are done?"

"I deduce that it won't," Xie Chengzhou said, "but deduction is not a conclusion."

"What's the difference?"

Xie Chengzhou thought for a moment, "Inferences are judgments I make based on existing data, and they could be wrong. Conclusions are the states after inferences have been verified, and the probability of them being wrong is even lower." He glanced at the numbers on his wrist, "What I need now is more data, not more inferences."

Li Gong didn't continue speaking. He bent his ring finger again, this time bending it all the way down without immediately straightening it. He stopped there and felt the sensation in the joint—there was sensation, a complete sensation, not the numbness before the repair, but a real, warm sensation, a sensation of slight tension in the ligaments when the joint was bent.

He spread his fingers.

"The dam keeper," he said, "fixed my hand."

"Yes," Xie Chengzhou said.

"Why?" Engineer Li asked. "Why does it need repair?"

Xie Chengzhou did not answer immediately. He had noted this question in his memo, but he had no answer. He only had one deduction: the dam keeper approved of the repair work, and Li Gong's finger injury was a byproduct of the repair work—the sap from the seepage workers—and had no direct relationship with the construction work itself, but the dam keeper still repaired it.

"Perhaps," he concluded, "it's not repairing your hand, it's repairing damage that appeared in the copy."

Engineer Li glanced at him.

"You mean, it doesn't care whose hand it is, it only cares if the hand is bad?"

"That's the idea," Xie Chengzhou said, "but it's just a deduction."

A gust of wind blew upwards, carrying moisture and that fishy smell. Xie Chengzhou pressed his feet firmly and felt the soles of his feet.

0.088 Hz.

The reduction continues.

At the thirty-second minute, the vibration disappeared.

It didn't slow down to zero; it just disappeared suddenly—0.07 Hz was still there, and then the next second, it was gone.

Xie Chengzhou put his foot firmly on the ground and felt it.

There was nothing there.

It wasn't the kind of disappearance where "it's gotten weaker, I can't feel it anymore," it was truly gone. The ground beneath his feet was clean, and the low-frequency vibration that had been there since he entered the instance, the 0.1 Hz he had felt in the corridor, on the dam, and in the management room, had completely vanished.

He paused in that feeling for about three seconds.

It took him three seconds to confirm that it wasn't a misjudgment on his part.

"It's gone," Old Zhao said.

He didn't ask Xie Chengzhou; he felt it himself. Thirty years on construction sites had made him more sensitive to the vibrations beneath his feet than Xie Chengzhou, except he wasn't using Hertz; he was using experience.

Xie Chengzhou did not speak immediately.

He glanced at the numbers on his wrist.

Water level: 5.90 meters. Distance from warning line: 2.10 meters.

Rate of increase: 0.001 meters per minute.

It's almost stopped.

He mentally went through the chain of reasoning, verifying each link: Repair behavior → Seepage agent retreat, verified. Seepage agent retreat → Larger individuals slow down, verified. Larger individuals slow down → Water pressure transmission slows down → Rise rate decreases, verified. Larger individuals leave → Water pressure transmission stops → Rise rate approaches zero, currently being verified, data supports this.

Every link in the chain is intact.

He paused for a moment in his mind before uttering the conclusion, because there was one last step that hadn't been verified: once the maintenance was complete and the cracks were sealed, the leaks would not return.

Eight minutes left.

"The water level is rising at almost zero," he said. "Wait eight minutes."

Old Zhao picked up the thermos, shook it, and heard the sound of hot water inside. Then he put the thermos back without opening it.

Li placed his hands on his thighs, no longer bending his fingers. He looked downstream from the dam, at a place where nothing could be seen in the darkness, for a while, then looked away.

"Where did it go?" he said.

"Upstream," Xie Chengzhou said, "or in deeper water."

Will it come back?

"I don't know," Xie Chengzhou said, "but it won't come back before we leave."

"How did you know?" Engineer Li said, not questioning, but genuinely asking.

"Because the crack has been repaired," Xie Chengzhou said, "there's no reason for it to come back."

Li Gong didn't ask any more questions.

He understood this logic—he had worked on water conservancy projects for twenty years, he knew what "without reason" meant, and he knew that the impact of a structure on the external environment was different before and after repair. The seepage particles approached the dam, possibly due to water pressure changes caused by the cracks, possibly due to the seepage itself, or possibly due to some mechanism he didn't understand—but whatever the reason, once the cracks were repaired, the triggering condition for that mechanism disappeared.

He went through this logic in his mind without saying a word.

Forty minutes have passed.

Xie Chengzhou stood up, walked to the template, squatted down, and began to loosen the nut of the first expansion bolt.

He drove the nut in himself, and he remembered the torque when he drove it in. Now he loosened it in the opposite direction, and the feel was right. The nut was turning, and it didn't get stuck or seized because of the mortar seeping in. This means that the mortar did not flow back out of the bolt holes when the template was sealed.

He removed the first bolt and set it aside, then the second, and the third.

Old Zhao squatted down next to him, held the other side of the template, and after he removed all the bolts, the two of them moved the template outward together—not by pulling it directly, but by pushing it outward a little first to make sure that the template and the dam surface were not stuck together, and then slowly removed it.

The template has been downloaded.

The cracks were exposed.

The mortar is grayish-white and has solidified. There are slight shrinkage marks on the surface, which are traces left by the slight volume shrinkage of the quick-drying mortar during hydration. This is a normal phenomenon and does not affect the seal. The direction of the crack is still there, but the crack itself is filled with mortar. The original black gap that could be seen to the bottom is now a grayish-white solidified line, with a width similar to the crack. The edges on both sides are connected to the original concrete surface without obvious gaps.

Xie Chengzhou held the flashlight close to the crack and shone the beam along the mortar line.

Dry.

There was no dampness, no seepage, and no sign of water gushing from the mortar surface. He stretched out his finger and ran it along the edge of the mortar line—rough and slightly warm, the temperature of the solidified mortar after the hydration reaction was complete, the residual heat from the exothermic chemical reaction that had not yet completely dissipated.

Not wet.

He placed his finger in the middle of the mortar line and felt it.

The numbness in his right index and middle fingers was still there, but he could feel the temperature of the mortar, the rough surface, and the density after it solidified—this density was correct, not hollow, not the feeling of the surface solidifying while the inside was still slurry, but solid, the feeling of the mortar solidifying after filling every gap inside the crack under pressure.

"Okay," said Engineer Li beside him.

There's something in the sound.

It wasn't excitement, nor was it a sense of relief; it was that feeling you get after doing something you know you did right, a feeling you don't need anyone to tell you, you just know it yourself. It was the conclusion drawn at this moment from the judgment accumulated over twenty years of water conservancy projects.

Xie Chengzhou pulled his hand back from the mortar line.

He mentally reviewed the final link in the chain of reasoning: maintenance was complete, the cracks were sealed, and the leaker had no reason to approach.

Data: Cracks sealed, verified. Seepage has not returned, verified (large individuals disappeared, the group retreated upstream, no new signs of approach).

Final step: Verified.

The chain is complete.

In his memo, he wrote: "Construction rule change · Verification complete · Full chain: Repair behavior → Seepage creature retreat → Large entity slows down → Water pressure transmission slows down → Increase rate decreases → Maintenance complete → Cracks sealed → Threat entities will not return · Full chain verification time: Approximately 45 minutes · Note: Is the rule change permanent? Does it persist after leaving the instance? To be verified in the next instance."

He closed the memo and stood up.

Water level: 5.91 meters.

Rate of increase: 0.0005 meters per minute.

It's basically stopped.

"You can go now," he said.

Old Zhao had already stood up, gathering the templates together, stacking them two by two. His movements were steady, not because he knew whether they were still useful or not, but because this was how he had finished work for the past thirty years—regardless of whether they were still needed, he would put away the tools, return the materials to their place, and leave no trash on site.

Li coiled up the hose of the grouting machine, fastened the buckle, and carried it on his back. He used his left hand to tighten the strap, fastening it firmly without hesitation, his ring and little fingers working together with full strength.

Xie Chengzhou collected the remaining mortar bags, tied them up, and carried them on his shoulder.

The three of them started walking towards the top of the dam.

The slope of the dam is 1:2.5, with an inclination angle of 22 degrees. Walking uphill is more strenuous than walking downhill. You have to keep your feet firmly planted and your center of gravity stable, otherwise you'll easily slip on the rough surface of the exposed aggregate. Xie Chengzhou walked at the back. He firmly planted his feet and felt the concrete of the dam surface, the rough surface of the exposed aggregate. It was cold, stable, and there was no vibration under his feet.

Clean.

Only the weight of the concrete and the sound of their three footsteps could be heard.

"You knew this would happen?" Old Zhao walked in front without turning around, his voice carrying behind him.

"I deduced that this would be the case," Xie Chengzhou said.

"What's the difference?" Old Zhao asked.

Xie Chengzhou took a few steps. "Knowing is the conclusion, inference is the process. The conclusion can only tell you that you did it right this time, but the process can tell you how to do it next time."

Old Zhao didn't say anything.

After a moment of silence, Old Zhao said, "I don't record the process."

Xie Chengzhou did not answer immediately.

He was pondering the meaning behind Lao Zhao's words. It wasn't "I don't understand the process," nor "I don't need the process," but rather "I don't remember"—a proactive choice, not a matter of ability.

He wanted to ask one more question: what did Lao Zhao remember?

But he didn't ask.

Because Old Zhao had already continued walking forward, his stride and rhythm unchanged, as if he had finished speaking and that was the end of it, with no follow-up and no need for one. Xie Chengzhou followed, and neither of them spoke again, each walking on their own. The slope of the dam lay beneath their feet, and the wind blew upwards, scattering the conversation, leaving nothing behind, yet not entirely nothing at all.

After walking for a while, Lao Zhao took the thermos off his waist, shook it, and found that there was still hot water inside. Then he hung the thermos back up without opening it.

Xie Chengzhou glanced at this action.

He recalled the pause in Chapter 53 when the dam keeper inspected Old Zhao's thermos—two seconds. The dam keeper's fingers touched the cup, paused for two seconds, and then let it pass. It wasn't a tool, but he let it through. Then, in the battle, Old Zhao poured hot water on the seepage creature, which shrank drastically and retreated into the crack.

heat.

The dam keeper paused because he sensed the heat. The seepage flow retreated because of the heat. Are these two events caused by the same mechanism, or by two different mechanisms?

He added a line to his memo: "Thermos cup · heat · dam guards pause · seepage flowers retreat · inference: heat is a key variable in this copy · source: unknown · to be verified."

"What are you writing down?" Engineer Li asked from beside him.

"A detail," Xie Chengzhou said, "a detail I hadn't noticed before."

"What details?"

"It's hot," Xie Chengzhou said. "It's Lao Zhao's thermos."

Engineer Li thought for a moment, "You mean... the dam keeper checking the thermos cups, and the people experiencing seepage being afraid of hot water—are these two things related?"

"It's possible," Xie Chengzhou said, "but it's also possible it's not. This is a deduction, not a conclusion."

Li Gong didn't ask any more questions.

As they reached the top of the dam, the wind picked up, carrying moisture and the open air from downstream. It was no longer the stuffy, stagnant smell of the dam surface; it was flowing, strong, the kind of wind you can only feel when you're standing at a high place.

Xie Chengzhou paused for a moment and took one last look at the numbers on his wrist.

Water level: 5.91 meters. Rate of rise: 0.

Distance from the warning line: 2.09 meters.

He memorized the number, then looked up and walked forward.

The ground beneath my feet was clean, only concrete and wind.