I'm doing engineering in the instance.

Feng Bo completed the level only after the sun had fully risen.

Xie Chengzhou roughly estimated the time; about forty minutes had passed since the three of them cleared the checkpoint. Forty minutes later, Feng Bo walked around inside for another forty minutes, checked what he'd said were "two more places," and then came out.

The exit light flashed, and then Feng Bo walked out.

He was holding something in his hand.

It wasn't a notebook; the notebook was in the inside pocket of his work clothes. What he was holding was a stone, about the size of a fist, held in the hem of his work clothes, and leaned slightly forward as he walked, a posture to prevent the stone from falling out.

Xie Chengzhou stood up and walked over.

"What are you holding?"

Feng Bo unfolded the hem of his work clothes for Xie Chengzhou to see.

ore.

This wasn't ordinary dam foundation rock—the dam foundation was made of granite, which Xie Chengzhou had seen in the corridor; it was grayish-white, coarse-grained, and typical of South China granite, with a geological background consistent with that. But the rock in Feng Bo's hand wasn't. It was a deep green, almost dark green, with a metallic luster—not matte, but the kind of sheen only found in rocks containing metallic minerals. Reflecting the morning sunlight, it looked as if someone had embedded a thin layer of copper in the stone, but it wasn't copper; it was the color of the mineral itself.

The weight is also incorrect.

Xie Chengzhou didn't take it, but just glanced at it and estimated its density by sight. This stone, by volume, was heavier than a normal silicate rock, at least one-third heavier. It had the density of a rock containing heavy metal minerals. It was not granite, not sandstone, not any kind of rock that should exist in this geological context.

"Where did it come from?"

"The corridor," Feng Bo said, "is located near the entrance of the expansion joint, embedded in the joint between the dam foundation and the corridor floor slab. It wasn't naturally embedded; it was placed there by someone."

Xie Chengzhou glanced at him.

How can you be sure that someone put it in there?

"The joint width," Feng Bo said, "is designed with a fixed width. This stone is three millimeters thinner than the joint width, so it was stuffed in, not naturally grown there. Naturally grown veins wouldn't have this shape." He flipped the bottom of the ore with his thumb. "Moreover, the bottom has cutting marks, not natural fracture surfaces, but tool cuts, straight, with neat edges."

Xie Chengzhou took the ore and held it in his hand.

It was heavy. A little heavier than he had anticipated, the kind of weight that makes you instinctively adjust your grip when you pick it up. It wasn't very heavy, but it was heavier than its appearance suggested. The surface was cold, the kind of cold that comes from spending a long time in the corridor, different from the cold of the dam's concrete surface. It was a cold from deeper inside, the temperature of the underground space.

He turned the bottom over and looked at it.

The cutting marks are real. There are two parallel cutting lines, about eight millimeters apart, with neat edges. They are not natural breaks, but marks left by some kind of cutting tool. The lines are straight and of uniform depth, which is the result of skilled operation.

He returned the ore to Feng Bo.

"What kind of mineral is this?"

“Chromite,” Feng Bo said, “high copper content, this is the color and luster, but that’s not the point.” He held the ore back in his palm. “The point is that this mineral doesn’t exist in this geological context. It’s a product of hydrothermal deposits, which require specific geological conditions. This area doesn’t have those conditions, so this ore didn’t come from here.”

"Someone brought him in."

"Someone brought it in," Feng Bo said. "It was placed in the expansion joint, in the most difficult-to-find corner of the corridor. It wasn't just placed there randomly; it was placed intentionally."

Xie Chengzhou remained silent.

He mentally processed the information, feeling its weight—heavier than the ore itself.

Someone placed a piece of ore that didn't belong in the instance, in a location that wasn't easily visible, cut it with a tool, and stuffed it into the seam of the expansion joint. This wasn't generated by the instance; it was something someone left behind in the instance, something they deliberately placed there after entering.

"You need to take it out."

Feng Bo did not answer, but tucked the hem of his work clothes back in and held the ore steady.

This is not an answer, this is the answer.

After reviewing the instructions, Xie Chengzhou said, "Taking it out will increase the weight. I haven't verified this variable regarding carrying items when clearing customs."

"I know."

"You know that, but you still have to bring it."

"But this is evidence."

After saying those four words, Feng Bo stopped talking, offering no explanation or persuasion. He held the ore in his hand and looked at Xie Chengzhou.

Xie Chengzhou did not respond immediately.

He waited for Feng Bo to continue, but Feng Bo did not.

"Evidence," Xie Chengzhou said, "is evidence only if someone sees it. You don't know if it will still be there after you take it out, or who you'll show it to. Right now, all you have is a stone that might cause problems with your passage through customs."

Feng Bo glanced at him.

"Yes," Feng Bo said, "I don't know if it's still there after I took it out."

He paused for a moment.

The wind in the open field came from the north; it was dry and without moisture. When it blew, you could feel the moisture being taken away from your skin, and your lips felt a little dry. The sun had already risen, and the light was flat, the low-angle morning light, casting long shadows on every stone in the open field and making the metallic luster of the ore in Feng Bo's hand even more obvious.

"But I know," Feng Bo said, "that if I didn't bring it, it would definitely be gone."

Xie Chengzhou remained silent.

He went through this logic in his mind, looking for loopholes.

"If I don't take it, it will definitely be gone"—this means that every time the instance resets, the item status inside is reset, and it's uncertain whether the ore will still be there the next time you enter; but if you take it out this time, you at least have one chance to confirm that it's real, that it can cross the instance boundary, and that it's evidence. The risk of taking it out is uncertainty, while the cost of not taking it is certainty.

He couldn't find the loophole.

But he hasn't said "okay" yet.

He glanced at Feng Bo's cuffs.

The light gray mineral powder mark was still there, fine and even. It wasn't something he picked up after clearing the dungeon this time; it was left when he was cutting ore. It was left when he used tools to cut it in the corridor. It was left after he entered this dungeon for the third time, found the ore, went back to prepare tools, and came in for the fourth time specifically to retrieve it.

This was not a spur-of-the-moment decision.

This is a researcher collecting evidence.

"Okay," Xie Chengzhou said.

Feng Bo glanced at him, neither saying thank you nor nodding, but simply weighed the ore in his palm again to make sure it was steady.

Xie Chengzhou opened the memo and wrote: "Feng Bo: Ore · Chalcocite · Non-local geological background · Artificial cutting marks · Expansion joint · Someone put it in · Third set of footprints · Carrying non-prop items to pass through: First time · Result: To be verified."

"You like to take notes," Feng Bo said.

Xie Chengzhou didn't respond to that sentence. He finished writing the last word and closed the memo.

"You can bring the props out," Feng Bo said. "I've seen them; I cleared the game, and the props were still there. This isn't a prop, but I want to know if the result is the same."

Xie Chengzhou suppressed this information and remained silent.

He closed the memo.

Feng Bo carefully scooped the ore back into the hem of his work clothes and held it in his hand.

"Do you know what this means?" Feng Bo said, "Someone put something in the dungeon that doesn't belong here."

"I know," Xie Chengzhou said.

"It wasn't placed there by the prototype," Feng Bo said. "The prototype doesn't need to place a real ore. The prototype can generate it directly. This ore is real. It was brought in from a real place and placed there. Someone entered this instance and did this."

Xie Chengzhou suppressed those words in his mind for a moment.

The ore was brought in from a real place. This means there's some kind of passage between the instance and the outside world, which not only players can enter and exit, but items can also enter and exit. Moreover, someone is using this passage to do something, and has done it more than once—the first time was to put the ore in, and the second time was for Feng Bo to bring it out.

"What do you plan to do with it?" Xie Chengzhou asked.

"Bring it into Yuan City first," Feng Bo said, "and find someone to take a look at it."

"Who should I look for?"

"Someone knows," Feng Bo said. "I'll let you know if I find out."

He didn't say who it was.

Xie Chengzhou didn't ask any more questions. He wrote the blank in his memo, marked it with a "️", and then put the memo away.

The sun rose higher, the angle of the light changed, the shadows on the open ground became shorter, and the metallic luster on the surface of the ore changed direction, from reflecting light from the front to reflecting it from the side. The color looked darker and greener, like a color you wouldn't normally see on a construction site.

Feng Bo steadied the ore and walked towards the edge of the open space. His steps were even, and the sound of his feet hitting the ground was rhythmic, just like the rhythm he used when walking on the dam.

He took a few steps without turning back and said, "You guys go to Yuan City first, I'll be there later."

Then he continued walking, heading towards the other side of the open space, not the direction Xie Chengzhou and the others had come from, but another direction, as if he knew a different path.

Old Zhao watched him walk away, tucked his thermos into his waistband, and said, "This person," he paused, "is not simple."

"It's not simple," Xie Chengzhou said.

The three of them headed towards Yuan City.

Xie Chengzhou took a few steps, paused, and looked back at the platform. The inscription on the platform was still there: "Site #004 - Completed".

He walked forward.