612 meters to the coolant reservoir.

Speed: thirty-four kilometers per hour.

They had enough braking power for one stop.

Mira kept her hand on the brake switch and stared into the end of the headlight beam. The new track descended along a grade absent from the map and ran toward a circular bulkhead in the coolant reservoir.

“What if we stop now?” Yona asked.

“We never move again.”

“And if we don’t?”

“We go through that wall and into the water.”

Distance remaining: 547 meters.

Ian was pressing his temples. Blood from his nose had reached his lip.

“Where does the track go?” Mira asked.

“I don’t know.”

“You said it changed to go inside the factory.”

“I heard that. Now there’s too much.”

“Too much what?”

“Water. Machines. Rina.”

Mira did not ask more. Ian was not reading a map. He was hearing signals mixed together.

An alarm sounded from the cargo car.

Rina’s heart rate: 146.

Nutrient-solution osmotic concentration falling.

Daniel’s voice came over the communicator.

“Mira, slow down.”

“If I do, we stop here.”

“Every time the tank shakes, the pressure in her lines rises.”

“If we stop, I don’t know whether there’s any route we can walk from here.”

“It’s still better than driving into a reservoir.”

Distance remaining: 403 meters.

Mira pressed the brake switch.

Metal screamed against metal. People pitched forward. The culture tank slid four centimeters and tore one floor anchor free.

Daniel caught the tank with his body.

“Rina!”

The fluid surged to one side. Rina’s shoulder struck the glass.

Speed: twenty-nine.

Twenty-four.

BRAKE BATTERY TEMPERATURE ABOVE LIMIT.

Mira kept holding the switch.

Sparks from the right wheel rose to window height.

Speed: thirteen.

The train stopped forty-one meters before the coolant bulkhead.

Darkness returned.

BRAKE BATTERY REMAINING: 0.

AVAILABLE TRACTION POWER: 0.

Pavel Jin, a citizen selected by lottery, had split his forehead open. Sarah checked his pupils, then immobilized his neck.

Mira opened the cab door. The smell of overheated metal and damp air came in. This was an internal Forge sector beyond the purified-air network. The oxygen display had fallen to 18.7 percent.

Yona switched on a portable light.

“How long can we last?”

“We didn’t use the train’s air batteries for propulsion. Six hours.”

“With the door open?”

Mira closed it.

“Two and a half.”

Daniel shouted from the cargo car.

“Sarah!”

One of Rina’s connection lines had folded where it pressed against the securing frame. Sarah straightened the tube, but the flow indicator did not return.

“Auxiliary circulation is blocked.”

“Fix it.”

“The pump is running. Tissue may have grown inside the line.”

“What if you remove it?”

“We have to open the tank.”

Rina opened her eyes.

“Don’t open it.”

Sarah brought her face close to the glass.

“If we leave it like this, circulation on the right-lung side will be inadequate.”

“How long?”

“At the current reading, the pain becomes severe within twenty-three minutes. After that, I don’t know.”

“How long to get outside?”

“We have to find a route first.”

Rina looked down at the folded line.

“Open it outside.”

Daniel said, “What if we never make it outside?”

“If you open it here, I can’t go.”

Daniel could not argue.

Mira climbed down the ladder at the front of the train. The rail did not end at the bulkhead. It disappeared beneath the floor. Blue coolant filled a shallow channel, and the rails continued under the surface through the circular door.

Yona shone her light into the water.

“This track was built to drive an entire coolant carrier into the reservoir?”

“Probably for coolant freight cars.”

Beside the bulkhead was an old manual control panel.

COOLANT INTAKE.

EMERGENCY DISCHARGE.

EXTERNAL HEAT-EXCHANGE ROUTE.

A physical seal had been added over the last item.

FORGE PRODUCTION-LINEAGE PROTECTION.

Mira opened a diagram box beneath the controls. Paper and thin metal sheets had fused together in the damp. Yona peeled them apart one by one.

Inside the reservoir, the current rail split in two. One line entered beneath Production Line Two. The other was an abandoned route to an outer-wall heat-exchange tower.

“There is a way outside,” Yona said.

“It’s sealed.”

The abandoned route had been closed seventeen years ago.

REASON: REDUCED EXTERNAL HEAT-EXCHANGE EFFICIENCY / SPORE INTRUSION / HEAT-EXCHANGE PLATE CORROSION.

REPLACED BY: INTERNAL COOLANT CIRCULATION.

The manual lever that opened the line stood on the opposite side of the reservoir. Water depth: 2.3 meters.

“Swim over and pull it?” Yona asked.

“Pulling it won’t make the train move.”

An emergency-discharge procedure was written beneath the diagram.

It used the difference in reservoir level to force coolant through the external heat-exchange route. When the discharge turbine turned, it supplied eleven minutes of power to the abandoned rail.

Creating a twenty-eight-meter level difference required dumping 2,740 tons of coolant. Line Two’s remaining cooling time would fall to sixteen hours, and the probability of losing the crystal seed would rise to sixty-eight percent.

Yona read the figures.

“So the people can get out, and the factory might die.”

“There are twenty-three people in that factory too. Don’t compare numbers alone.”

Mira had no answer.

Amin Kore connected to the train. His video shook, alarms flashing behind him.

“We have confirmed the train’s location.”

“Did you change the track?” Mira asked.

“A Forge carrier modified it four years ago. To avoid corrosion on the outer-wall line, the route was integrated with coolant freight.”

“Passenger maintenance trains use the same rail. Why wasn’t the map updated?”

“There was no plan to carry passengers.”

“There is now.”

Someone shouted behind Amin.

“Axle temperature seventy-four!”

The Sector Nineteen blower feed opened at the same time. Sena was pushing the inner race of the new bearing onto the shaft. It jammed halfway.

Time remaining: 00:05:31.

“I told you not to use a hammer,” Mira said.

“I’m not.”

Sena wrapped more heating strip around the race.

“The shaft is deformed. The bearing spec is right, but it won’t seat.”

Amin said they should have sent the spare axle as well. Sena snapped that with enough people they could have moved an eighty-six-kilogram axle.

“Grind the shaft surface,” Mira said. “Outer six-tenths of a millimeter.”

“That’ll make it eccentric.”

“It already is. We can’t make a perfect repair. Make it survive one day.”

“And after one day?”

“Whoever is alive then fixes it again.”

Sena picked up the grinder.

Blower time: 00:04:48.

“If you activate emergency discharge, Line Two is unlikely to survive,” Amin told Mira.

“Another route?”

“Have the train passengers disembark and use the upper walkway over the reservoir.”

“What about Rina’s tank?”

“Leave it.”

Daniel opened the connection.

“Who decided that?”

Amin could not see him. Only Rina’s tank status was on his screen.

“The loss of one transitional life-form is outweighed by loss of the production lineage—”

“Say her name.”

Rina’s voice entered through the wall vibration.

Amin stopped mid-sentence.

“Rina So.”

“Say it again.”

“Rina So must remain behind.”

“Why?”

“The culture tank cannot pass the walkway.”

“I know that now.”

“Emergency discharge would damage the possibility of producing computing substrates used to control air and power for thousands of people.”

“I know that too now.”

“Do you still choose to go outside?”

Rina curled slightly against the pain from the kinked line.

“Yeah.”

Amin looked at Mira.

“Are you deciding this?”

“No.”

“Then are the sixty people on the train deciding the future of twenty-three Line Two workers and the city?”

“Not that either.”

“Who decides?”

Mira looked at the manual lever across the reservoir.

“The people whose hands are touching the consequence.”

“Is that your definition of authority?”

“No. It’s the shape of the time we have.”

The sentence sounded like philosophy the instant she said it, and Mira regretted it. Words did not move water.

She handed the safety line from her belt to Yona.

“I’m going in.”

“With that arm?”

“A lever doesn’t need two arms.”

“And if you get caught underwater?”

“Pull.”

“Excellent plan.”

Yona tied the rope around her own waist.

Mira expected the coolant to be cold. It was lukewarm. Heat returned from Line Two lingered at the bottom of the reservoir. When she stepped into the channel, the water rose to her ribs. Coolant seeped into the wound on her left arm. Pain climbed from her arm into her neck.

“Contamination?” Mira asked.

Sarah checked a portable monitor.

“High metal particulates. Don’t put an open wound in it.”

“Too late.”

Mira drew a breath and submerged.

The underwater lever was bound in ceramic sealant. The cutter could not bite it. Running out of air, Mira tugged the line twice and Yona hauled her up.

“Can’t cut it.”

“Another tool?”

Noah took the short pry bar from the pouch Rahim had thrown them.

“This is for releasing a rail switch.”

“It won’t break ceramic.”

Ian started down beneath the train.

“Stay there,” Mira shouted.

He stopped.

Mira heard her own voice. She had forbidden him before asking again.

“I don’t know what you’ll hear near the water. If you still want to come down, tie on a safety line.”

Ian thought about it.

“I won’t come down.”

“Okay.”

“But listen to Rina.”

Rina had her eyes closed in the tank. A white thread extending through the cargo-car drain touched the coolant surface. Its tip moved with the ripples.

“Right,” Rina said.

“What?” Mira asked.

“There’s an empty space below and to the right of the lever.”

Sarah said, “The biological line may be sensing pressure vibration through the water. We do not know its accuracy.”

“Rina, is that something you feel, or something Bloom is sending?”

“I don’t know.”

“Then you don’t have to use it.”

Rina opened her eyes.

“I said I want to.”

Mira nodded.

“Below and right. That’s the only thing I’ll trust.”

She entered the water again.

There was a two-finger gap below and to the right of the lever. Mira inserted the pry bar and reached with her injured left arm as well. Blood drifted from the wound as the ceramic cracked.

She pushed again.

The seal broke and the lever snapped free.

The entire reservoir shuddered.

Mira lost the safety line. The current pulled her toward the bulkhead. A shard of ceramic scraped her thigh.

Yona hauled the rope.

The knot tightened around Mira’s waist. Her face broke the surface.

As she coughed out water, the emergency-discharge alarm began.

COOLANT DISCHARGE: 4.2 TONS/SECOND.

LINE TWO COOLING REMAINING: 15:57:11.

CRYSTAL-SEED LOSS PROBABILITY: 71 PERCENT.

ABANDONED RAIL POWER: 00:10:59.

Blue light came alive in the power line beneath the train wheels.

Workers moved behind Amin’s screen. Some cursed Mira. Others ran to close cooling valves.

“We are not abandoning Line Two,” Amin said.

“I didn’t ask you to.”

“You reduced our time to sixteen hours.”

“Fix it within sixteen.”

“We don’t have the parts.”

“You have people.”

“People cannot manufacture material from nothing.”

“I know.”

Mira climbed back onto the train.

“So record what I took away.”

Amin did not answer.

The train moved again.

A reservoir gate opened. Blue water rushed away beneath the rails. The wheels cut through the water. Inside the circular bulkhead, the switch blade slowly seated toward the abandoned line.

POWER WINDOW: 09:32.

OUTER WALL: 1.8 KILOMETERS.

The train entered the tunnel.

On the Sector Nineteen screen, Sena put down the grinder.

The new bearing slid fully onto the shaft.

“Turn it.”

Workers pushed the manual start handle.

The blower turned once.

On the second rotation, the shaft wobbled.

On the third, one blade grazed the housing.

The warning clock reached zero.

The motor started.

A long metallic sound continued.

Mira watched the screen and waited.

Airflow: nineteen percent.

Twenty-seven.

Forty-one.

Shaft vibration: 230 percent of tolerance.

“It won’t last a day,” Sena said.

“How long?”

“Eight hours. Twelve if we’re lucky.”

Pressure began recovering in Residential Sectors Six and Eight.

The city had not lost its air today.

But Semiconductor Line Two now had a sixteen-hour deadline.

The train reached the lower outer wall by way of the abandoned rail.

Power remaining: 02:14.

Two doors stood ahead.

An inner pressure door and an external heat-exchange door.

The space between them was wide enough for the culture tank. This had not been a human airlock. It was an industrial discharge bay for coolant.

“The inner door should close automatically when the outer one opens,” Yona said.

Mira looked at the inner hinges. White breath-stalks had grown through every gap, thickened rapidly by the rain.

“It won’t close automatically.”

“Remove them?” Noah asked.

“No time. Once the train is inside, close the inner door by hand first.”

The train entered the chamber.

The inner door descended behind them. White stalks compressed and leaked pale fluid. The door stopped thirty-eight centimeters above the floor.

Power remaining: 01:31.

Twelve people pressed against the door and pushed.

It did not move.

Mira cut breath-stalks with the insulated cutter. Every time she severed one, another was squeezed farther into the gap.

Power: 00:58.

The outer door required forty-two seconds to open.

“We have to start now,” Yona said.

“The rear isn’t sealed.”

“If power dies, neither door moves.”

Elias’s voice came through.

“Delay opening the external door.”

Mira kept cutting.

“Reason?”

“Inner-door seal integrity is seventy-one percent. Opening the external door will depressurize Sectors Four, Six, and Eight together.”

“How far?”

“They may fall below respiratory safety thresholds within six minutes.”

Sena cut in.

“If I raise blower output any farther, the blades break.”

Outer-door power: 00:41.

“Rina has less than ten minutes,” Daniel said.

“What about the survivors on the train?” Elias asked.

Sarah answered, “Two hours of air, but Rina’s auxiliary circulation has to be opened within eight minutes.”

“There are 4,800 people in the three city sectors.”

Yona put a hand on the outer-door control.

“Numbers again.”

“If we do not say the numbers, people disappear,” Elias said.

Mira lay flat beneath the inner door and looked back toward the city. The tunnel continued through the thirty-eight-centimeter gap. Air was already flowing in that direction.

“Tell the people in those three sectors.”

“There is no evacuation time.”

“Tell them anyway.”

Elias activated a public alarm.

POSSIBLE OPENING OF OUTER-WALL INDUSTRIAL DISCHARGE BAY.EXPECTED PRESSURE LOSS: SECTORS 4, 6, 8.MOVE TO INTERNAL SEALED ROOMS.ESTIMATED PREPARATION TIME: 36 SECONDS.

Demands not to open the door and demands to open it arrived together. Someone said there were children in Sector Six. Someone else said they could not move.

Mira took the outer-door start handle.

“Are you deciding?” Elias asked.

Mira could not see the faces behind the messages. Only names and sentences flowed past.

“Yes.”

“I will record the result.”

“Record it under my name.”

She pulled the handle.

OUTER DOOR STARTING.00:42.

POWER SUPPLY REMAINING: 00:33.

The times did not fit.

Power would fail before the door was halfway open.

“Dump more coolant,” Yona said.

Amin objected immediately.

“No.”

“We need nine seconds.”

“Additional discharge drops Line Two below twelve hours of cooling.”

Mira pushed the emergency-discharge lever one step farther.

COOLANT DISCHARGE: 6.8 TONS/SECOND.

LINE TWO COOLING REMAINING: 11:43:02.

OUTER-WALL POWER: 00:51.

The door rose.

Rain poured through the first opening. Outside air carried in the smells of soil, metal, and rotting leaves. People on the train cried out.

Through the gap beneath the inner door, dry city air escaped in the opposite direction. White breath-stalks swelled as they met outside moisture, splitting under the door and widening the opening.

SEAL INTEGRITY: 54 PERCENT.

Thirty-nine.

SECTORS 4, 6, 8: PRESSURE FALLING.

Sena raised blower output.

Shaft vibration: 310 percent of tolerance.

“I can’t push it higher!”

The outer door rose high enough for the culture tank.

Yona and Noah, wearing filters, went out first. Outside oxygen was 19.1 percent, but metallic particulates were 4.7 times the limit and spore levels exceeded the measuring range. The monitor approved only short exposure.

Yona raised a hand.

“Keep it open!”

The cargo restraints came free. Daniel, Sarah, and three workers pushed the culture tank. One wheel caught on the outer-door threshold.

Rina’s heart rate: 158.

Auxiliary circulation: stopped.

“We have to lift it,” Daniel said.

Six people put their shoulders beneath the tank.

Mira tried to join them. Her left arm would not rise.

“Get out,” Daniel said.

“I can—”

“Take Ian outside.”

Mira looked at Ian.

Blue lines under his wrist were pulsing toward the rain.

“Do you want to go out with me?” she asked.

Ian looked at Rina.

“Push first.”

Mira used her right hand against the back of the tank.

The wheel crossed the threshold.

The tank tilted, then settled.

Rina left City Seven’s outer wall for the first time.

Sarah immediately opened a service port. Daniel raised waterproof sheeting and Yona blocked the rain. White tissue had grown inside the kinked line. Sarah showed it to Rina.

“I have to cut this to restore circulation. It could be a sensory line.”

“What do I lose if you cut it?”

“I don’t know.”

“And if you don’t?”

“Your right-lung function may be damaged.”

Rina tried to look outside, but the rain sheet blocked her view.

“Open it a little.”

Daniel lifted the sheet.

Under a gray sky, black ground spread away from the city. Water ran along the outer wall. Farther out, among low ruins, white stalks bent and rose in the wind. Too sparse to be a forest. Too alive to be ruins.

A raindrop struck the culture-tank glass.

“Cut it,” Rina said.

Sarah severed the tissue line.

Rina’s body curled. Daniel lifted a hand toward the glass, then stopped.

“Can I touch?”

With her eyes closed, Rina put her palm against the inside.

Daniel placed his hand over the same spot.

Auxiliary circulation rose from twelve percent.

Twenty-one.

Thirty-seven.

Inside the train, people were arguing again over who received the nine filters. The outer door was open, but people without filters stopped at the threshold.

Mira put the last filter on Ian.

“What about yours?” he asked.

“I’ll close the door and come out.”

“It doesn’t even close. I’ll stay too.”

“No.”

The word came out first. Ian shook his head.

“You decided again.”

Outside, Rina tapped the glass.

“Ian.”

He looked between the open door and Mira.

Pressure in the city continued falling.

A report came from Sector Six: one sealed room closed. Capacity 312. Another 1,040 people still moving.

Maren appeared from Sector Eight.

“We closed the pressure door at the water-recovery plant. Eighty-six people are in here.”

“Breathing time?” Elias asked.

“Six hours. We have water.”

Sector Four did not respond.

Mira looked at the manual release shaft beside the outer door. If they closed the door, there would be no power to open it again. Even if it sealed, Rina and everyone already outside would be unable to return.

Outside were nine filtered people and Rina in the culture tank.

Inside were Mira and more than fifty people without filters.

Ian stood between them.

“Tell me what you want,” Mira said.

“I want to go outside with Mom and Rina.”

“Someone has to close the door.”

“I’ll go back,” Noah said from outside.

Mira looked at his injured hand.

“The manual shaft takes two and a half turns.”

“I’ll use my left.”

Mira did not answer.

Noah crossed the threshold again.

“This time, if I do it wrong, tell me.”

He fitted the pry bar into the manual shaft.

Mira took Ian outside.

She had no filter. Yona removed her mask and handed it over.

“Three breaths, then give it back.”

Mira put it on and inhaled three times. She held the fourth breath and returned the mask.

The outside air was cold.

Noah turned the shaft.

The outer door began to descend.

The inner door remained thirty-eight centimeters open. City air rushed through the narrowing gap, but once the outer door closed the loss could stop.

The people who remained on the train were trapped in the outer-wall staging chamber. They had two hours of air battery and a powerless train that could no longer return to the city.

Halfway down, white breath-stalks rose between the rails.

“It’s caught!” Noah shouted.

Mira started back under the door.

Ian grabbed her arm.

“You told me to go out.”

“Noah can’t close it alone.”

“I decided I wanted all of us outside.”

Mira could not pull her hand from his.

Noah released the pry bar and picked up the cutter. His right-hand bandage turned red again. He held the stalks in his left hand and pressed the cutter with his right.

One.

Two.

The door descended again.

Noah’s face remained visible through the final gap.

“Once it closes, the staging-zone pressure will hold.”

“What about you?”

“I’ll stay inside.”

“Why?”

“I chose.”

The door closed.

Not perfectly.

Seal integrity: ninety-one percent.

Pressure in the three city sectors stopped just above the danger line.

Sector Four reported thirty-seven people with hypoxia symptoms. Two were unconscious. No deaths had yet been confirmed.

The Sector Nineteen blower continued to turn on its temporary bearing.

Semiconductor Line Two had eleven hours thirty-one minutes remaining.

The people outside could not move far from the wall. Mira held her breath without a filter, then accepted Yona’s mask again.

The portable sensor warned:

OXYGEN 19.3 PERCENT.SPORES: 18× LIMIT.METAL PARTICULATES: 5.1× LIMIT.

The rain was weakening.

Mira removed the mask and took one short breath.

Soil. Wet iron. Mold. And a sweetness she had never smelled before.

Her throat stung immediately. She coughed and handed the mask back.

“You can breathe it,” Yona said.

“For how long?”

No one answered.

Ian crouched beside rainwater. A white film floated on the surface of a puddle. Before he touched it, Mira caught his wrist.

This time Ian did not get angry.

“Look,” he said.

Tiny black specks beneath the white film scattered with each raindrop, then gathered again. They were not merely avoiding the wind.

They moved out of Ian’s shadow toward the light.

A white thread from Rina’s culture tank passed through the glass drain and reached the outside. When its tip touched the puddle, every black speck stopped at once.

A moment later, the specks began moving—not toward the outer wall, but toward distant ruins.

The portable sensor confirmed a biological response and failed to classify either its type or risk.

Beneath the warning appeared the estimated remaining life of the filters.

00:43:17.