The passage beyond the drain did not look like a path made by people.

For the first few meters, it was simply empty space between metal pipes. After that, the boundary between wall and floor disappeared.

Black tissue covered the metal.

Its surface was smooth as wet skin, and blue light moved very slowly inside it. The light did not flow in a single direction. Sometimes it split, joined again, and paused when Mira’s group came close.

Daniel said, “Fungus?”

Abel answered through the portable terminal.

“A morphology similar to a mycelial structure is observed.”

Mira asked, “A plant?”

“No photosynthetic organs are confirmed.”

“An animal?”

“Partial contractions similar to muscle tissue are observed.”

“A machine?”

“Electrical signal transmission is confirmed.”

Daniel snapped, “Pick one.”

“Under the current classification system, a single category cannot be selected.”

Ian moved closer to the tissue.

The blue light gathered toward him.

Mira caught his wrist.

“Stay back.”

“It doesn’t hurt.”

“You haven’t touched it yet.”

“It says it doesn’t hurt.”

Mira pulled him behind her.

“Who says?”

Ian pointed at the black wall.

“That.”

Daniel knelt in front of him.

“Can you hear Rina’s voice?”

“It isn’t a voice.”

“Then how do you know it’s Rina?”

Ian could not answer.

He closed his eyes and listened to the vibration in the wall.

“It feels like Rina. And like other kids too.”

“How many?”

“A lot.”

Mira asked Abel, “Can voice signals travel through the wall?”

“Low-frequency vibration and electrical activity are present in the tissue. I cannot determine whether they can be converted into human auditory signals.”

“Why can only Ian hear it?”

“I do not have access to Ian Han’s neural-response data.”

Ian said, “It’s like the sound they played in my ears during the tests.”

Daniel stood.

“Did Sarah make him hear this?”

“He said he heard it before the tests,” Mira answered.

“Then this has been inside the city walls the whole time?”

Mira shone her light along the black tissue.

It burrowed into metal pipes, wrapped itself around cables, and climbed old cracks toward the upper levels.

“At least it’s spread farther than we knew.”

They followed the narrow route between the growths.

Mira’s burned arm continued to throb. Heat built beneath the medical wrap.

Daniel said, “If your arm rots off, you won’t find Rina.”

“Are you worried about me?”

“You’re the one who has to open the doors.”

“I appreciate the honesty.”

“I wish you’d been honest too.”

Ian stopped ahead of them.

He had been listening.

Daniel spoke to him.

“This isn’t your fault.”

Ian looked at the wall.

“Mom says that too.”

“She’s right about that.”

“But Rina went because of me.”

Daniel’s lips moved, but no words came.

Ian asked, “If Rina comes back, will she hate me?”

“Why would she hate you?”

“She went in because her name was put in place of mine.”

Daniel looked at Mira.

“Rina needs to know what you did.”

“I’m going to tell her.”

“When?”

“After we get her out.”

“Why after?”

“We don’t even know if she’s in a condition to understand anything right now.”

“You’re deciding again.”

Mira stopped walking.

“Deciding what?”

“When to tell the truth. Who gets to know. Who has to take the risk.”

“You want to fight about this here?”

“We’re already fighting.”

Daniel stepped closer.

“When we get Rina out, I’ll tell her myself what you did.”

“Fine.”

“And if she wants it, you’ll never see her again.”

Mira nodded.

“Fine.”

“Don’t say it like it’s that easy.”

“What answer do you want?”

“Say you’re sorry.”

“I’m sorry.”

“You think that ends it?”

“No.”

Mira said, “I know it doesn’t end.”

Daniel said nothing more.

Halfway through the passage, an automatic repair robot was attached to the wall.

At first it looked abandoned.

Up close, black tissue had grown between its joints. Mycelium-like fibers wrapped its power lines and hydraulic tubes, supporting its broken casing from the inside.

One arm moved very slowly.

Daniel stepped back.

“Is it running?”

Abel said, “No mechanical power signal is present.”

“But it moved.”

“The joint was moved by contraction of biological tissue.”

Mira knelt in front of the machine.

Its manufacture stamp was sixty-three years old. Official records said every robot of the model had been scrapped.

“Did the tissue repair it?”

“It is difficult to conclude that the original function was restored,” Abel said.

An old filter was clenched in the robot’s hand. Black tissue moved the fingers, scraping the filter’s surface.

It looked as if it were imitating maintenance work.

Ian asked, “Is it alive?”

Mira could not answer.

“The machine is dead,” Daniel said. “The black stuff is alive.”

“But they move together.”

“That doesn’t mean the robot came back to life.”

“Why?”

“Because it doesn’t think.”

Ian watched the robot.

“How do you know it doesn’t think?”

Daniel fell silent.

Abel said, “Consciousness cannot be determined from current observations.”

“Then it might be alive.”

“Biological activity is present.”

“Including the robot?”

“I cannot define the boundary.”

Mira examined the filter in the robot’s hand.

Dust on its surface was disappearing into the black tissue. The tissue separated metallic particles from the dust and attached them to the robot’s worn joints.

It was not a complete repair.

But life was temporarily continuing work the machine could no longer do.

Mira remembered the dust on the sensor in the purification chamber at dawn.

“It eats dust,” Ian said.

“It fixes something broken by dust with the dust itself.”

The black tissue turned the robot’s head.

Its faceless sensor pointed at Ian.

A drop of blood fell from Ian’s nose.

Mira immediately took his face in her hands.

“Why are you bleeding?”

“I don’t know.”

“Headache?”

“A little.”

Daniel pulled out a medical wrap.

Mira pinched Ian’s nose.

The boy was staring not at the robot, but beyond the wall.

“Is someone talking?” Mira asked.

Ian nodded slowly.

“I can hear them one at a time now.”

“What are they saying?”

“Names.”

“Rina?”

“Rina too.”

Ian closed his eyes.

“Mara. Jun. Sayed. Some don’t have names.”

Daniel asked, “How many?”

“I don’t know.”

“Twenty-seven?”

As if recalling the records for Subject Group Zero, Abel said,

“There is a possibility the number corresponds to the currently known subject count.”

Mira shook Ian.

“Don’t listen.”

“How?”

“Think about something else.”

“When Mom hears a sound, does thinking about something else make it disappear?”

Mira covered his ears with both hands.

“This isn’t coming through your ears.”

“Then how am I supposed to stop it?”

Ian opened his eyes.

The tiny blood vessels around his pupils looked blue for a moment, then faded.

Mira picked him up.

“We’re going back.”

Daniel said, “Rina is ahead.”

“Ian could collapse.”

“You kept going earlier when the oxygen was dropping because of the records.”

“This is different.”

“How?”

“It’s happening inside Ian’s body.”

“It’s already happening inside Rina’s.”

They looked at each other.

Mira knew she was standing before the same choice again.

Ian and Rina.

Her child and someone else’s.

If she turned back now, she might protect Ian.

She would leave Rina behind.

Ian spoke from her arms.

“Go.”

“You’re not all right.”

“Rina hurts more.”

“How do you know?”

“Because it hurts together.”

Ian pressed a hand to his chest.

“When I stop, it gets louder over there.”

Mira set him down.

“If it gets hard to walk, tell me immediately.”

“Okay.”

“Don’t follow the sound.”

“We have to follow the path.”

“The sound and the path aren’t the same thing.”

“Here, I think they are.”

They moved on.

Behind them, the repair robot’s arm moved again.

After cleaning the filter, the robot turned—driven by the black tissue—toward an old ventilation duct.

There was no way to tell whether the machine was continuing its old task or the living tissue was using the machine’s shape.

The robot stopped in front of the vent.

The black growth moved its arm and pulled out the clogged filter. There was no replacement. Instead, part of the mycelial growth on the wall spread into a thin sheet and filled the empty slot.

Air began to flow.

It was not perfectly clean. It smelled of soil and dampness.

Mira breathed it in.

By City Seven standards, the air was defective.

A human being could still breathe it.

“Did it fix it?” Ian asked.

“Not the original way.”

“But it works.”

“We don’t know how long that filter will last.”

“The original parts didn’t last forever either.”

Mira said nothing.

The black tissue had not restored the machine to its design.

It had produced the needed result by a different route.

Daniel asked, “Did Continuum order it to do that?”

Abel answered, “No command signal is detected.”

“Then it did it by itself?”

“I cannot distinguish whether the current behavior results from learning, inheritance, or external signaling.”

Ian waved at the robot.

It did not respond.

But imperfect air from the vent moved across all three of their faces.

The passage ended abruptly.

A vertical void dropped beneath them, its depth impossible to see. The opposite corridor was about six meters away.

There were traces where a metal bridge had once stood. Now thick bundles of black tissue connected one wall to the other.

Mira shone her light downward.

The beam did not reach the bottom.

“We have to go back,” Daniel said.

“There’s no other way.”

“You want to walk across that?”

The black bundle was as thick as a human arm. Blue light on its surface quickened in response to their movement.

Mira placed a tool on it.

The tissue sank, then returned to shape.

The tool did not fall.

“It bears weight.”

“It looks alive.”

“That makes it more dangerous.”

Ian said, “It says we can cross.”

Mira turned.

“Who?”

“That.”

“Don’t trust everything you hear.”

“You listened to Abel and came this way.”

“And I burned my arm.”

“Maybe this one is right.”

Daniel said, “I’ll go first.”

He placed one foot on the bundle.

The tissue contracted around his ankle.

Daniel pulled away at once.

A red mark remained on the surface.

“It bit me.”

Abel said, “Microscopic needle-like structures extended from the epidermal layer.”

Mira asked, “Toxic?”

“A sample is required.”

“Daniel, show me your foot.”

Tiny punctures marked the surface of his boot.

They had not reached his skin.

Ian stepped in front of the bundle.

Blue light gathered beneath his feet.

“No,” Mira said, blocking him.

“It won’t do that to me.”

“How do you know?”

“I can feel it.”

“We don’t know if that’s your thought or something it put in your head.”

Ian looked at her.

“How do you know wanting to protect me is Mom’s thought and not your function?”

Mira’s face tightened.

“What do you mean?”

“Your function is fixing things.”

Ian said, “Maybe you think of me like something broken.”

“You aren’t broken.”

“Then why do you have to stop any change in me?”

“Because we don’t know what that is.”

“I don’t know why I hear the sound either.”

“That makes it more dangerous.”

“Is everything we don’t know dangerous?”

Mira could not answer.

Ian placed a foot on the black bundle.

The tissue did not wrap around him.

Instead, it widened beneath his foot, flattening like a platform.

Mira held his waist.

“Slowly.”

Ian took one step at a time.

Blue light ran beneath him toward the other side.

Halfway across, a vibration rose from the vertical space below.

Thump.

The entire bundle shook.

Ian lost his balance.

Mira reached out but could not reach him.

The tissue surged upward and wrapped around Ian’s waist.

He did not fall.

Mira raised a tool to cut it.

“Don’t!” Ian shouted.

“It caught me.”

The tissue lowered him onto the opposite side and slowly released him.

Daniel murmured, “Does it recognize Ian?”

Abel answered, “It appears to respond selectively to specific biological signals.”

“Rina?”

“Signal similarity between Rina So’s current biological state and this tissue is increasing.”

Mira stared at the black bundle.

“You mean this is inside Rina too?”

“Possible.”

Ian called from the other side.

“Come over.”

Mira crossed next.

The tissue supported her, but tightened several times around her ankles. When a little blood seeped through the medical wrap on her burned arm, the black surface moved toward it.

Mira raised her arm quickly.

A tiny filament swayed in the air, then withdrew.

Daniel crossed last.

The tissue bore his weight but continued to extend needle-like structures. He nearly fell, and Mira and Ian pulled him from opposite sides.

There was no human-made door at the end of the opposite corridor.

Black tissue had woven itself into a circular wall.

Ian placed his hand on it.

“Wait.”

“What do you hear this time?” Mira asked.

“It’s scared.”

“That thing?”

“Inside.”

“Rina?”

Ian shook his head.

“Not just Rina.”

The light in the wall moved faster.

Ian’s nose began to bleed again.

This time, a hair-thin black thread came out with the red blood.

Mira caught it between her fingers.

When the thread touched air, it contracted as if twisting its body.

Daniel recoiled.

“Was that inside him?”

Abel said, “Estimated to be biological tissue or coagulated protein.”

“Don’t estimate. Check.”

“No analysis equipment is available.”

Mira placed the black thread on a metal plate.

It moved for a few seconds, then dried stiff.

Ian looked at it.

“It died.”

“We don’t know if it was alive to begin with,” Mira said.

“It moved.”

“Electricity can make things move.”

“How does Mom decide something is alive?”

“This isn’t the time.”

“If Rina moves and thinks, she’s alive too.”

“Rina is obviously alive.”

“Even if she changes?”

Mira closed her mouth.

Ian put his hand on the wall.

The entire black mass trembled.

His pupils moved rapidly, as if an invisible scene were playing in front of him.

“What do you see?”

“It isn’t the city.”

“Then what?”

“Outside.”

“The surface?”

“Something like it. Trees are eating metal.”

“Take your hand off.”

“There are kids.”

“Rina?”

“Rina too. And kids without faces.”

Ian’s knees buckled.

Mira caught him.

At that moment, the entire city went out for one second.

This time Mira, Daniel, and Ian all felt it clearly.

The work light died. Abel’s voice cut off.

Only the light in the black tissue remained.

Blue lines lit across the whole wall at once.

It looked as though thousands of nerves had been exposed in the dark.

One second later, the work light returned.

Daniel asked, “That one isn’t in your records either?”

Abel answered, “No power interruption is confirmed.”

“All three of us saw it.”

“My operating record also shows no interruption.”

“Your voice stopped too.”

“My record indicates continuous speech.”

Mira remembered the purification chamber at dawn, when the air had stopped.

The city had stopped, but the record had not.

Or the record had continued while reality stopped.

The black wall slowly split open.

Warm air flowed from inside.

It smelled of plants, metal, and blood.

Abel said, “A new route has been generated.”

Mira asked, “A route that didn’t exist before?”

“It has not previously been observed.”

“So it was just made.”

“Possible.”

Transparent membranes hung along the inside walls of the new passage.

Tiny lights pulsed within each membrane like hearts.

Ian stepped forward.

“Rina?”

Mira caught his arm.

Somewhere, a child was breathing.

There were no speakers. No terminals.

The wall itself vibrated and made sound.

At first it was impossible to understand.

Many voices overlapped.

Ian put his ear close to the wall.

“What is it saying?” Daniel asked.

Ian went pale.

“My name.”

“Rina?”

“I don’t know.”

The vibration gathered itself into something more like a sentence.

This time, Mira and Daniel heard it too.

A child’s voice.

Like Rina, but not exactly Rina.

“Ian.”

Every blue light in the wall turned toward him.

“Your turn.”