Underground Pipe Network Layer

Regarding the backflowing energy, Lu Yuan and Bolen had no good solutions for the time being. For now, they could only observe.

The sixth night arrived quickly. The light from the city wall runes in the distance dimmed once more. Tonight, the ghouls attacked again, though fortunately, their numbers were small.

Only a handful of them emerged from the hole, crawling along the fungus-covered area toward the defensive position. They were all in a state of absolute starvation, skeletal and rib-thin, their eyes filled with a desperate craving for flesh.

Bo Er and his men dealt with them easily. There were only a dozen or so; it didn't take much effort.

However, this was not a good sign. After two nights of silence, whatever was on the side of the abyss was resuming its probing attacks. It was merely extending a 'tentacle' to see if the defensive line still held.

Lu Yuan stood at the second-floor window, watching as Bo Er's men dragged the ghoul carcasses onto the copper ground to let them corrode on their own. In the distance, sporadic gunfire from other positions echoed briefly before falling back into silence.

Bolen remained at the site, testing the grey-green backflow every two hours. The substance flowed steadily along the section of copper pipe he had repaired, its direction and concentration unchanging. It showed almost no fluctuation, whether in concentration or flow rate, remaining nearly identical. It was as if something were controlling it with precision.

After the third check, Bolen began to frown. Natural contamination backflow should not follow such a pattern. Given how chaotic the things in the abyss were, it should logically surge like a tide. Yet, the contamination inside the copper pipe was far too uniform. If they hadn't happened to repair this section of the pipe, they would never have known.

Hopefully, Glock, who had taken this intelligence into the inner city, would find some leads.

The horizon began to pale. Footsteps approached from the side. It was Bolen.

"Come take a look. This seems to be good news," Bolen signaled for Lu Yuan to approach.

"Oh?"

Lu Yuan walked over and crouched down. Bolen's finger was sliding slowly along the surface of the copper pipe.

"When I repaired this pipe yesterday, I only noticed the internal corrosion and that the copper plates had been disturbed."

He stopped his finger, pointing to a tiny protrusion on the pipe wall.

"But during last night's monitoring, I discovered a problem."

He glanced at Lu Yuan.

"The contamination is too stable."

Lu Yuan frowned.

"I measured it every two hours, and the six results were almost identical," Bolen said in a low voice. "Have you ever seen something like this? The contamination from underground couldn't possibly be this uniform, unless..."

"Unless the source isn't the area underground, or something is controlling it."

"Correct," Bolen nodded. "That's why I pondered it for a while last night."

He tapped along the protrusion.

"And then I thought, I might have been mistaken about something. This section of copper pipe itself is wrong."

Lu Yuan leaned in to look. The yellowish, blackened bronze piping meant nothing to him.

"What's wrong with it?"

"These are replacements," Bolen said quietly. He used his cane to draw two lines on the ground.

"The original conduction pathways of the city wall were laid when the city was built. The copper material and the inscription style match the city wall; every stroke was chiseled by hand."

He pointed to the copper pipe beneath their feet.

"But this pipe clearly doesn't match."

He looked up.

"Someone removed this section of the original pathway and replaced it with one they cast themselves."

Lu Yuan's gaze darkened.

"Could it not be for repairs? If not... what about the alignment?"

Bolen stood up and tapped the pipe wall with his cane. He crouched back down, placing his palm on the wall and sliding it slowly along the alignment.

"I've studied the Bronze City inscriptions carefully; their paths are easy to guess, but this section is different."

His finger stopped at a bend in the pipe.

"It deviates downward, extending toward the ground. It's not connecting to the outer city, but heading in a certain direction deep underground."

Lu Yuan paused.

"Where do you think this pipe leads?"

Bolen was silent for two seconds before standing up and brushing the rust from his hands.

"I don't know, but it absolutely cannot be the abyss underground."

He turned around, his gaze fixed on the distance.

"Think about it. When we went down to the abyss last time, we saw foundation-level copper pillars. The inscriptions were even older than those on the city walls. Those things were definitely built with the city."

Bolen continued, "With that level of inscription and copper density, whatever they are sealing must be catastrophic. Even a mere overflow would be too much for a copper pipe of this thickness to withstand."

"Unless..."

Lu Yuan understood what Bolen meant.

"Unless it's not coming directly up from the abyss."

"Exactly," Bolen nodded. "The end of this pipe likely isn't in the abyss, but somewhere else underground, where a contamination source exists."

He tapped the ground with his cane and pulled out a roll of parchment. It was densely packed with drawings of the general layout of Bronze City. Bolen pointed to a spot on it.

"But if someone created a new contamination point above the seal, such as in the underground pipe network layer of Bronze City, then even the strongest seal would be useless."

"Underground pipe network layer?"

"Yes. There is a network of pipes beneath Bronze City: sewage, rainwater, evacuation tunnels, storage rooms... it's all in there."

"And I estimate this pipe follows the direction of that underground network."

Bolen was silent for a few seconds.

"I need to go down and see. I'll track the pipe's path. Once I'm on site, I'll know for sure."

Lu Yuan looked at him without speaking.

Bolen hesitated for a moment, then added, "I'm very interested in this contamination that can corrupt copper. Naturally, the Nightwatchers cannot just leave it be."

Lu Yuan finally nodded upon hearing this.

"We'll wait until daytime."

"Understood."

The night passed quickly. After confirming there were no ghouls, Lu Yuan had Bo Er arrange for some Nightwatchers to maintain surveillance at the collapse site. As for the rest, they would go with him.

The target was an inspection port behind a partially collapsed stone wall, three hundred meters behind the collapsed defensive line.

It was a cast-iron cover, less than a meter in diameter, embedded in a groove in the copper floor. The cover was covered in a thick layer of scavenger fungus, with the grey-green fungal layer cementing the iron lid to the surrounding copper plates.

Seeing this, Lu Yuan felt a sense of foreboding. He had Bo Er scatter copper powder around the edge of the lid.

A hissing sound erupted, and the fungal layer curled and fell away rapidly. Kail used a copper crowbar to pry the lid open.

The rusted iron lid let out a dull, snapping sound, and a damp, cold wind carrying a strange stench surged up from the hole.

After a moment, Lu Yuan looked down into the vertical shaft. Iron ladders were embedded in the shaft walls, extending four or five meters downward. He swept his gaze downward.

【Environmental Perception: Small amount of pollution source detected...】

"Right, did we notify the Alchemy Workshop about our entry into the underground pipe network?" Lu Yuan turned to look at Bo Er.

"We did. The personnel participating in this operation have also been reported: myself, Captain Lu, Bolen, Kail, and two other brothers."

Those two brothers were veterans. One was a grizzled soldier missing half his left pinky finger, and the other was a nimble young man. A total of six people.

They had two sandworm oil lamps, four canisters of spare oil, one canister of fire powder, two bottles of mithril, two canisters of copper powder, and various other supplies.

"Move out. Descend."

Following Lu Yuan's order, the group entered one by one.

The shaft was not deep. They reached the bottom in just over four meters. Their boots landed on the damp stone bricks with a dull thud.

The sandworm oil lamps were lit, and a pale white light diffused outward.

Before them lay a passage about two meters wide, with brick walls on both sides and an arched copper frame at the top. The floor was made of stone bricks, with water seeping through the cracks and accumulating in a shallow layer.

The air was damp and cold, turning their exhaled breath into white mist.

Bolen's first action was not to look at the path, but to touch the copper frame on the wall.

"The copper's conduction effect is still here! Things don't look as bad as I thought."

Bo Er said at this moment: "The underground pipe network is very safe. The City Hall used to have dedicated personnel for maintenance, and many people even lived down here. And if I remember correctly, there should be a separate lighting system..."

Bo Er didn't finish his sentence, because as far as the eye could see, everything was pitch black. There was no sign of the so-called lighting system.

Lu Yuan, meanwhile, was holding his lamp and looking at both sides. Every three or four meters, an iron lamp holder was embedded in the wall. They were petal-shaped and should have held fluorescent stones or oil lamps, but they were all empty now.

Some holders had only the base left embedded in the wall. The upper sections had been snapped off at the waist and lay toppled to the side. The broken surfaces of the iron petals were jagged, showing signs of being bent and snapped by force.

The traces looked very similar to the way the ghouls had snapped the lamp posts on the surface.

"The ghouls did this," Bo Er whispered.

Lu Yuan didn't reply. He was looking at something else. On the wall to the left of the passage, about a meter high from the ground, there was a dark red smear.

The trail extended from ahead, winding in an arc along the wall, and finally disappeared into the shadows of the corner.

It was blood. Very old blood. It had dried completely, turning into a thin, dark red film that was almost black. But the shape of the trace explained everything.

"Move."