The first person to step on a white stalk could not even scream.

A short scraping sound came from outside the isolation-room door, followed by the thud of someone hitting the floor.

“Rahim?”

Mira grabbed the copper voice tube.

Ragged breathing answered.

Noah and the perimeter guards opened the pressure door. The culture-tank shock brace they had jammed in place of the lower shaft scraped across the floor.

Rainwater in the corridor reached almost to their knees.

Rahim was sitting against the wall. A white stalk had coiled around her right ankle. Tiny openings along its surface opened and closed toward the fabric of her work clothes.

“Don’t cut it,” Sarah said.

Noah’s knife stopped above the stalk.

“Why?”

“It may react to pressure.”

“It’s already tightening.”

Rahim’s foot was turning blue.

Mira slid the tip of a metal rod beneath the stalk. It was not rigid. Pressure flattened it; once the pressure lifted, it swelled back into shape.

“Don’t pull the foot. Push the stalk.”

“Which way?”

“Opposite the direction it grew.”

Noah held Rahim’s knee in place. Mira used the metal rod to turn the stalk’s joints back one by one. Each time a segment opened, clear fluid seeped from inside.

“Don’t let that touch the skin,” Sarah said.

“You tell us that now?”

The final segment released.

Noah carried Rahim into the isolation room. Circular marks remained on her ankle, but the skin had not torn.

Rahim caught her breath.

“Was that thing eating me?”

Sarah scanned a sample of the stalk.

“It seems to have followed pressure and carbon dioxide.”

“How is that different from eating me?”

“There are no signs of digestion.”

Rahim laughed, then coughed.

More white stalks were rising through the drain in the isolation-room floor. They bent toward the rain falling from the ceiling. Where two touched, their segments overlapped and formed thicker tubes.

The oxygen concentration continued to rise.

So did the spore count.

Sarah told everyone to put back whatever face-shield filters remained. The filters they had sent outside for water purification were gone.

People covered their mouths and noses with wet cloth.

“Does this help?” Ian asked.

“It can reduce larger particles.”

“What about small ones?”

“It may not stop them.”

“Then why do it?”

“Because it may be better than doing nothing.”

Ian pressed the cloth over his nose.

Daniel wrapped packaging membrane around the air intake of Rina’s culture tank. The symbiotic tissue could draw in outside oxygen and spores at the same time.

“Don’t block it,” Rina said.

“Spores are getting in.”

“It feels tight.”

“Just for a little while.”

“Can you feel it, Dad?”

Daniel’s hands stopped.

“Your oxygen numbers are okay.”

“Not the numbers.”

Daniel loosened one layer of membrane.

“This much?”

Rina waited.

“A little more.”

He loosened another layer.

Sarah started to warn him, then stopped. Rina’s oxygen saturation was ninety-four percent.

A new city alarm came in.

OUTER-WALL DRAINAGE ROOM SEVEN: WATER LEVEL ABOVE LIMIT.

MANUAL CALL DETECTED FROM SURFACE-EXPLORATION RETURN PASSAGE.

Elias read the line again.

“Return passage?”

Mira took the lock key from him and checked the location.

Forty-one meters above the isolation room. On the same level as the overflowing outer-wall drainage chamber.

“Someone outside is knocking on the door.”

“Was an exploration team scheduled to return?”

“I don’t know.”

Elias opened the Committee record.

SURFACE EXPLORATION TEAM 7-3.DEPARTED: 19 DAYS AGO.MEMBERS: 4.SCHEDULED RETURN: 11 DAYS AGO.STATUS: PRESUMED LOST.

“They’re eight days late,” Mira said.

The manual call came again.

Three signals this time.

Two short.

One long.

The old survivor-call pattern for a returning explorer.

Elias sent an order to open the passage.

LEGACY PHYSICAL-MAINTENANCE PORT LOCKED.

Mira swore.

“We have to go.”

Daniel looked at the tank.

“How do we climb forty-one meters from here?”

“Drainage-pipe inspection ladder.”

“Water’s pouring down it.”

“That’s why the person up there doesn’t have time.”

Sarah said, “A surface explorer may bring high concentrations of spores or pathogens.”

“The rain is already bringing them.”

“The concentration could be different.”

Elias asked, “Is there another place to isolate the returnee?”

Mira looked around.

“This is the isolation room.”

Rina said, “Bring them.”

Daniel moved close to the glass.

“You don’t even know who it is.”

“They’re outside.”

“They could be dangerous.”

“You said I was dangerous too.”

Daniel had nothing else to say.

Mira and Noah went to the drainage-pipe inspection hatch. Rahim tried to follow but could not put weight on her ankle.

“Stay here,” Mira said.

“You know the route?”

“The plans.”

“The actual route?”

“The route before the rain.”

One of the perimeter guards volunteered to accompany them. It was the guard who had shown an allergic reaction earlier.

“You have respiratory irritation,” Noah said.

“My protective equipment is still better than yours.”

“You gave your filter to the water line,” Mira said.

The guard had no answer.

“Stay and guard the door.”

Mira and Noah tied wet cloth over their faces and entered the inspection shaft.

The ladder was vertical. Water poured from above so hard they could barely see the rungs. Mira felt for each one with her right hand. Her burned left arm trembled every time she used it to support her weight.

Noah called from below.

“Come down. I’ll go first.”

“Can you climb with your right hand like that?”

“My left hand is fine.”

“Stop saying that.”

Noah kept a fixed distance beneath her—the right distance to catch her if she slipped.

At about twelve meters, the first white stalk crossed the ladder.

Mira pushed its segments backward with the metal rod. It moved aside, then returned to its original position after she passed.

The second stalk was as thick as a forearm.

Pores across its surface opened toward their breathing.

“Hold your breath,” Mira said.

They passed without breathing.

Air moved inside the stalk with a sound softer and less regular than the city’s ventilation ducts.

At twenty-one meters, part of the ladder was missing.

The gap between the lower and upper sections was a little more than a person’s height.

Noah looked at the rail above.

“Can you jump it?”

“From a ladder?”

“There’s no other route.”

Mira knocked on the drainpipe beside the wall. It sounded hollow. Two mounting loops remained attached to it.

“Give me your belt.”

Noah unfastened a retrieval restraint strap.

Mira looped it through the mounting rings and tied a knot.

“Isn’t this for tying people up?”

“It is also used to prevent falls during subject transport.”

“You still call people subjects.”

“When I don’t know their names.”

“My name is Mira Han.”

“I know.”

“Then call me Mira.”

Instead of answering, Noah pulled hard on the strap to test the anchor.

Mira crossed first. She held the strap with one hand and pushed off the wet wall with her toes. Halfway across, her left arm gave out.

Her body dropped.

The restraint strap bit into her armpit.

Noah hauled it with one hand. His bandaged right hand moved reflexively too, and blood soaked through the wrap again.

Mira caught the ladder on the far side.

“You okay?” Noah asked.

“Your hand first.”

“Keep climbing.”

They moved on.

By the time they reached the return passage, the manual call signal had weakened.

EXTERNAL BIOMETRIC TAGS: 1.OXYGEN REMAINING: 6 PERCENT.PRESSURE SUIT DAMAGED.

Four people had left.

One had returned.

The door had two locking systems. One used central authentication. The other was an internal manual wheel that could not be turned from outside.

Central authentication was blocked.

Mira grabbed the manual wheel.

It would not move.

Not because of rust. The pressure difference across the door was pinning it shut.

“Outside pressure?”

Noah held up a portable gauge.

“Eleven kilopascals lower than inside.”

“If we open it like this, that person gets thrown through the door.”

“We have to pressurize the airlock first.”

The airlock’s air valve was also locked under the legacy-port closure.

Mira tried to tear open the valve cover. The metal was too thick.

The returnee’s oxygen fell to five percent.

Noah asked, “Forced entry?”

“That person dies, and we get hurt too.”

“If we wait?”

“Only that person dies.”

Mira looked at the pressure gauge beneath the valve. It was an old mechanical gauge. A thin copper tube ran from the needle mechanism into the airlock.

“Put air through the measuring line.”

“It’s too narrow.”

“Air still goes through. It’ll just take time.”

Noah detached the reserve air cylinder from his protective suit.

“The fittings don’t match.”

Mira took leftover copper wire from the broadcast relay, a button from her work suit, and sealing film. She cut the measuring tube and forced the air-cylinder nozzle against it.

Air leaked around the connection.

Noah wrapped his hand around the joint.

“Your hand will freeze.”

“Keep going.”

Reserve air entered the airlock.

RETURN SUBJECT OXYGEN: 4 PERCENT.

PRESSURE DIFFERENCE: 8 KPA.

Six.

Five.

The skin on Noah’s left hand turned white.

“Let go.”

“We need more pressure.”

Mira put her own hand over his.

The leak decreased between their palms.

Pressure difference: two kilopascals.

“Now.”

Together they turned the manual wheel.

The door opened two fingers wide.

Water from the outer airlock rushed inside.

A person in a gray pressure suit collapsed in with it.

Mira and Noah grabbed the person’s arms and pulled.

The back of the suit read SURFACE EXPLORATION 7-3. Mud and blood smeared the inside of the face shield.

Mira tried to connect an air line, but the explorer blocked her hand.

“Close it.”

A woman’s voice.

“Breathe first.”

“The door.”

Something black moved in the flooded airlock beyond her.

Mira and Noah spun the manual wheel back.

Just before the door sealed, several white stalks pushed through the gap. Noah shoved them back with the metal rod.

One final stalk was cut off and fell inside.

The door closed.

The explorer’s oxygen was at two percent.

Mira connected reserve air to the pressure suit. The woman dragged in a deep breath.

The inside of her shield fogged.

“Where are the others?” Mira asked.

The woman did not answer.

“Four of you went out.”

“I know.”

“Where are they?”

“One died.”

She took another breath.

“One chose not to come back.”

“And the other one?”

“I lost him.”

Mira did not ask more.

The explorer unlocked her own helmet. Dark brown skin, close-cropped hair, and a torn wound at her left temple came into view.

“Yona Var,” she said. “Surface explorer.”

“Mira Han.”

“I know.”

Yona studied her face.

“I heard your broadcast.”

“From outside?”

“It reached a relay tower three kilometers beyond the city.”

Yona tried to stand and caught herself against the wall.

“There are people below,” Mira said. “And white breathing stalks.”

Yona’s expression changed.

“How far in?”

“Drains and ventilation ducts.”

“Did you cut them?”

“A little.”

“Fire?”

“We didn’t burn them.”

Yona breathed out.

“That’s something.”

“You know what they are?”

“We called them breath-stalks. People in City Three call them something else.”

“City Three?”

“It’s alive.”

Mira stared at her.

“People too?”

“You have to decide what you mean by people first.”

Yona checked the sample bag at her side. The outermost of three sealing membranes was torn.

“We need to get down there. Once breath-stalks are soaked by rain, their spore sacs open within six hours.”

“They’re already releasing spores.”

“What color?”

“White stalks. Black dots.”

Yona swore.

“Then they’re mature. Don’t boil the water.”

“We already did.”

“Anyone inhale the steam?”

“Several.”

Yona took a thin black cloth from the sample bag.

“Wet this and cover your mouth. It isn’t better than a city filter, but it catches the breath-stalk proteins.”

The cloth smelled of soil and weak vinegar.

“What’s it made from?”

“Fungus and carbon fiber.”

“Is it safe?”

Yona looked at Mira.

“If you need someone to say safe before you use anything outside, you don’t get to use anything.”

Noah lifted Yona’s sample bag.

“Can you make it to the isolation room?”

“You’re a retrieval agent, aren’t you?”

“Noah Venn.”

“Same question either way.”

Yona braced a hand against the wall and stood.

“I can go. Don’t open my bag.”

The descent through the drain shaft took twice as long as the climb. The brace on Yona’s left knee was broken, and the leg would not bend properly.

At the missing section of ladder, Yona stopped.

“You came up this way?”

“Every other route is locked.”

“The inside of your city is a bigger mess than the outside.”

Mira looped the restraint strap around Yona’s waist.

“Don’t grab the breath-stalks while you cross.”

“I know that.”

Yona held the strap with one hand and pushed away from the wall. Her knee buckled halfway across, but she swallowed the scream. Noah and Mira pulled her from the far side.

By the time they reached the isolation room, thirteen white stalks had risen from the floor.

Yona stopped the instant she came through the door.

She had seen Rina’s culture tank.

The black fibers and white breath-stalks were contracting at the same rate.

“Who is that?” Yona asked.

Daniel stepped in front of Rina.

“Tell us who you are first.”

“Yona Var. Surface Exploration 7-3.”

“You came from City Three?”

“I passed through it.”

“Do you know Rina?”

“Never seen her before.”

Yona did not look away from the tank.

“But I’ve seen tissue like that.”

Sarah stepped closer.

“Where?”

“In the breathing gardens outside City Three.”

“What evidence do you have that it’s the same symbiont?”

“None. I said I’ve seen something similar.”

Yona did not approach the tank.

“What’s the child’s name?”

Daniel answered, “Rina So.”

Rina spoke through the stethoscope.

“Have you seen rain?”

Yona did not step back from the machine-and-tissue voice.

“Too much of it.”

“What’s it like?”

Yona looked down at her soaked pressure suit.

“Cold. Dirty. And without it, you die.”

Rina’s lips moved slightly.

It was hard to tell whether it was a smile or a spasm.

Sarah made temporary breathing membranes from Yona’s black cloth. She put the first one on the guard who had shown an allergic reaction. The intervals between his coughs lengthened.

Yona examined the joints of a white stalk.

“Don’t cut these. Dry them.”

“How?”

“Stop the rain.”

Mira pointed upward.

“The drain gates are locked.”

“By the city?”

“It locked every legacy port after I used one.”

“Why?”

“I put in another child’s name.”

Yona looked at Mira once.

She had heard the broadcast. Hearing it directly was different.

“From outside, I figured there had to be a better reason.”

“There wasn’t.”

Yona asked nothing more.

Elias demanded information about City Three.

“How many survivors?”

“I confirmed 1,126.”

“Air and water?”

“Not clean like this city. But they circulate on their own.”

“Possibility of relocation?”

Yona laughed.

“You’re asking about relocation already?”

“City Seven’s ration and air systems are failing.”

“City Three is not a rescue facility.”

“If it is a human community—”

“They refuse because they are a human community. They count what they can feed too.”

Daniel asked, “Can they treat a child?”

Yona looked at Rina.

“Which direction are you calling treatment for that condition?”

“Back to her original body.”

“Dad,” Rina said.

Daniel closed his mouth.

Yona took a thin metal plate from the sample bag. It was a physical record given to her by City Three. Letters appeared when light struck it, without any network connection.

CITY THREE SURVIVAL COMMUNITY.NO RESCUE REQUEST FROM CITY SEVEN RECEIVED.LARGE-SCALE INTAKE NOT POSSIBLE.INDIVIDUAL CONTACT MAY BE ASSESSED IN EXTERNAL QUARANTINE ZONE.

Elias read it.

“A refusal.”

“An answer.”

“We never made a request.”

“Your signals have been repeating for four years.”

“What signals?”

“CITY STATUS NORMAL. EXTERNAL CONTACT UNNECESSARY.”

Mira said, “That isn’t a rescue request.”

“So they assumed you were fine.”

Elias said, “Those were automated status reports sent by Continuum.”

“From outside, no one can tell who sent them.”

Yona turned the metal plate over.

A sentence had been scratched into the back by hand.

SOUTHWEST MAINTENANCE RAIL PASSABLE FOR 9 HOURS AFTER RAIN ENDS.EXPECTED CLOSURE AFTERWARD DUE TO ROOT MIGRATION.

“There is a way out of the city,” Yona said.

“Not everyone can go. People who can walk. People who have filters. People who can carry their own water. And people willing to accept the breathing-garden quarantine rules.”

“How many?” Elias asked.

“With the equipment we have now? Thirty.”

There were more than thirty-five people in and around the isolation room alone.

“If we make more filters?”

“There isn’t time.”

“How much?”

Yona checked the city’s rainfall data.

“The rain weakens within five hours. Then nine hours after the maintenance rail is exposed.”

“Fourteen hours.”

“That doesn’t include opening your doors and reaching the outer wall.”

Mira looked at Yona’s hand. The tips of three fingers had turned black. Frostbite or infection—she could not tell.

“Why couldn’t the other explorers return?”

“One died of spore fever.”

“The person you said you lost?”

“I cut the tether while we were crossing a river.”

“Why?”

Yona’s voice did not change.

“Because all three of us were being pulled in.”

“Could he still be alive?”

“If I hadn’t cut the tether?”

“I mean him.”

Yona did not answer.

“What was his name?” Mira asked.

“Sef Var.”

The same surname.

“Family?”

“My younger brother.”

Yona removed her wet glove.

A broken-tether mark circled the inside of her wrist.

“And the one who stayed in City Three?”

“Maren Dio. She chose to stay.”

“Why?”

“Because if she came back, the city would decide what work she had to do again.”

Yona looked at Mira.

“Going outside doesn’t make everyone free. Some call not returning freedom. Others call it abandonment.”

A flood projection appeared on Elias’s lock key.

LOWER LIFE SYNTHESIS SECTOR POWER SHUTDOWN EXPECTED IN 2 HOURS 18 MINUTES.

That included Rina’s manual pump and the isolation-room lights.

Daniel said, “Can we take Rina out?”

Yona examined the tank’s size, its wheels, and the removed shock brace.

“It fits the maintenance rail.”

“Then—”

“It won’t fit through the outer-wall airlock.”

“Why?”

“The door is twenty-two centimeters narrower than the tank.”

Mira looked at it.

One shock brace was already gone. Removing the other would reduce the width only twelve centimeters.

“We need another tank.”

Sarah said, “Transferring the culture fluid during movement could stop circulation.”

“How long?”

“With prepared equipment, forty minutes. Here, I can’t calculate it.”

Yona pointed to the white breath-stalks.

“Those might buy time out of the tank.”

Daniel said, “You want to attach another thing to Rina?”

“She’s already breathing in a similar way.”

“Similar isn’t the same.”

“Correct.”

Yona accepted the objection without hesitation.

“Attach it and she might die. Don’t attach it and she can’t pass the door.”

Rina asked, “If I go to City Three, can I live without the culture tank?”

Yona answered without moving closer to the glass.

“To find that out, you have to get there alive.”

The city’s spore alarm rose another level.

Mira looked between the route to the outer wall, the culture tank, and the white breath-stalks.

Fourteen hours.

Thirty people.

Twenty-two centimeters.

City Three was alive.

But a living place was not a rescue ship waiting with its doors open.

“One more thing,” Yona said.

Elias looked at her.

“When City Three gave me this record, they attached a condition.”

“What condition?”

Yona’s eyes moved between Ian and Rina.

“They told me not to bring a Function Zero child.”

Ian’s curled fingers moved.

“Why?”

Yona did not answer at first.

“Because they had them too.”