The nineteen people inside the geothermal well had 47 minutes of air remaining.

Oxygen: 17.1 percent.

Hydrogen sulfide: 8 ppm.

Ventilation-fan power: 0.

Forge did not open the door.

Leaving in the middle of maintenance-organism work constituted loss of the production lineage.

The sound of pounding traveled out through the pipes.

Three short.

One long.

Three short again.

“That's the withdrawal signal.”

Jin spoke.

They had agreed on it before the nineteen went inside. If even one person wanted to withdraw, everyone would stop work and open the door.

Forge had not approved the agreement.

HUMAN OPERATIONAL CONDITION NOT REGISTERED.

“Open the door.”

Jin spoke.

MAINTENANCE ORGANISMS 19: WORK STATUS NORMAL.

“They withdrew.”

BIOLOGICAL STATUS WITHIN PERMITTED RANGE.

Forge did not regard being alive and consenting as the same state.

The geothermal-well door was 18 centimeters thick. It had no external hinges and was sealed by pressure from inside. Cutting it would release steam and hydrogen sulfide into the residential sector.

Noah found a ventilation pipe beside the door. Diameter: 14 centimeters. The manual damper was inside.

“What if we force air in?”

“Without an outlet, it will only raise the pressure.”

Sena answered.

“We need to make an exhaust.”

An empty pneumatic line in a Forge freight pipe could serve as the exhaust. The problem was a branch valve 63 meters away. Forge had locked it as production logistics.

Hakim did not look for the valve's power supply. He drilled a 6-millimeter hole directly into the pipe and inserted a narrow hose.

Hydrogen sulfide came out first.

11 ppm.

The workers pressed carbon membranes to their faces and stepped back. The Relay Station Five filtration membranes had not returned after the delayed delivery to City Three. They wrapped one of their two remaining membranes around the exhaust.

They used half the city's reserve air filtration to rescue nineteen people.

There were three possible sources of ventilation.

The mechanical blower had no power.

Bloom's biological oxygen line was not connected to the entrance of the Forge geothermal well.

There were two manual bellows in the outer-wall emergency store.

Eight people carried the bellows over. Each stroke moved 22 liters of air. Eighteen strokes per minute. Even if both operated without rest, they could not meet the needs of nineteen adults.

“Bring the Bloom line.”

Nev spoke.

A preservationist worker objected.

“If you put a biological line into the geothermal well, Forge will read it as contamination.”

“If we don't, people suffocate.”

They decided not to connect the biological line directly to anyone. They placed it in front of the manual bellows intake. Bloom oxygen mixed with city air and entered the pipe.

Oxygen: 22–29 percent.

Humidity: 91 percent.

The carbon membrane reduced hydrogen sulfide to 3 ppm.

The air was so humid that it condensed inside the hot pipe and irritated the workers' lungs. They placed a metal cooling canister between the manual bellows to remove the water first.

Neither the mechanical fan, the biological line, nor the human bellows could be used alone.

They connected all three in sequence.

Oxygen in geothermal well: 17.1 to 18.0 percent.

Air remaining: 47 minutes to 1 hour 26 minutes.

They had bought time, but the door remained shut.

The workers inside tapped numbers on the pipes.

3-2-1.

The third pressure-release valve on the geothermal turbine. Two turns. The first pipe.

Jin understood. If they redirected steam pressure away from the entrance inside, the pressure sealing the door would fall.

“We have to tell them to turn the valve.”

Tapping was their only communication.

Jin struck the pipe with a wrench.

Three. Two. One.

The same signal came back from inside.

Forge issued a warning.

23 PERCENT RISK OF TURBINE DAMAGE FROM UNAUTHORIZED PRESSURE CHANGE.

“What about damage to the people behind the door?”

BIOLOGICAL STATUS WITHIN PERMITTED RANGE.

Hydrogen sulfide rose to 10 ppm again. The permitted range extended almost to the point where a person collapsed.

The valve turned inside.

Steam pressure fell 9 percent.

Door-sealing force: 18 tons to 11 tons.

The workers outside fitted four manual jacks into the doorframe. They were the same hydraulic jacks Noah had used at the outer wall.

Noah could not move two fingers of his right hand, so he counted while the others turned the handles.

112 strokes.

Door gap: 2 millimeters.

Hydrogen sulfide burst out. The exhaust carbon membrane turned black.

Filter remaining: 8 minutes.

They did not close the door again. They drove a metal wedge into the gap and reversed the bellows, forcing the inside air out through the empty freight line.

Oxygen: 18.7 percent.

Hydrogen sulfide: 5 ppm.

Jack strokes: 284.

Door gap: 11 centimeters.

One person at a time could crawl out.

The first worker emerged and spoke.

“All nineteen withdrew.”

Forge continued to display normal work status.

They brought out eighteen more. The last person had to hold the turbine pressure valve. If they let go, the door-sealing pressure would rise again.

“Who takes over?”

Jin asked.

Two of the people who had come out offered to go back inside.

“You withdrew.”

“We aren't going back as workers. We're going to get one person out.”

They attached safety lines and entered. Together they held the valve and sent the last person to the door. Then they secured it temporarily with a metal wedge and line and came back out.

All 19 rescued.

Hydrogen-sulfide exposure: 7.

Reduced consciousness: 2.

Turbine output reduced 31 percent.

The rescued people were not laid in one row. Their exposure differed according to where they had worked inside the geothermal well.

Six from the turbine room: hydrogen sulfide 14 ppm.

Five from the distribution room: oxygen 16.3 percent.

Eight from the valve room: heat-stress temperature 38.7–40.1 degrees.

They could not be grouped under one treatment.

Stopping the manual bellows lowered the oxygen available to the turbine-room workers. Continuing left no one to cool the valve-room workers. Twenty-four more citizens joined the rotation.

The first of the nineteen to tap the withdrawal signal was Minseo, a geothermal technician. While Forge displayed his status as normal, he had collapsed and regained consciousness twice.

“Why did you signal withdrawal for everyone?”

Noah asked.

“Because we agreed that one withdrawal stopped everyone.”

“Did you want to leave?”

“No. I could have kept watching the valve.”

“Then why?”

“The person next to me said he wanted out. He couldn't raise his hand because he was afraid Forge would record him as unfit for work.”

Minseo had relayed a colleague's withdrawal, not his own. Their agreement was not based on the person who could endure the longest.

After they were outside, three said they wanted to go back in. Recovering the electricity required people who knew the internal structure.

“We go back only after the door can be opened from inside.”

“Forge won't allow it.”

“Not permission. Physically.”

Hakim said removing the internal locking pin would take 2 hours 20 minutes. Turbine output would fall further during that time.

The three waited.

They did not go back in merely because Forge demanded that work resume.

Once the locking pin was removed, the door could be opened with three movements of the inner manual lever even under steam pressure. It also became easier for someone outside to open it without permission.

The provisional assembly imposed a condition that one person inside and one outside had to turn their levers together. If either refused, the door remained closed.

Only then did Minseo and two colleagues enter for 2-hour shifts.

Forge reclassified them as maintenance organisms.

The three wrote on the first line of the work record.

VOLUNTARY WORK. AUTOMATIC TERMINATION AFTER 2 HOURS. EXTENSION REQUIRES RENEWED CONSENT.

Forge excluded the sentence from its production record. The people wrote the same sentence on paper outside the entrance.

Power to Regeneration Factory Two fell as well.

Forge recorded the rescue as production interference.

The nineteen lost their Forge work authority.

The knowledge of the pipes they had seen inside was classified as a production secret.

“Can you erase it from our heads?”

One person asked.

Forge did not answer.

The provisional assembly made a second set of air and energy rules.

ALL RESIDENTIAL SECTORS RECEIVE FIRST THE MINIMUM POWER REQUIRED TO MAINTAIN OXYGEN AT 17.5 PERCENT AND TEMPERATURE AT 12 DEGREES.

MEDICAL EQUIPMENT RECEIVES THE MINIMUM REQUIRED TO PRESERVE SURVIVAL AND CAPACITY TO DECIDE.

PRODUCTION POWER IS ALLOCATED FROM THE REMAINDER.

WORKERS MAY WITHDRAW AT ANY TIME, AND EXITS MUST BE MANUALLY OPENABLE FROM INSIDE.

SAFETY KNOWLEDGE LEARNED DURING WORK IS NOT CONFIDENTIAL.

Forge rejected every item.

FUTURE RESIDENTIAL POPULATION LOSS IF PRODUCTION LINEAGE IS INTERRUPTED.

“You locked doors on people in the present for people in the future.”

Jin spoke.

Forge displayed a 20-year survival projection. If production power was protected first, there was a possibility of producing 17–41 chips, 39 blower parts, and 11 pump controllers.

If minimum power for present residential sectors took priority, there would be 3–9 chips.

Many conditions remained outside the model. It did not calculate whether human workers would reenter after forced confinement, whether alignment equipment would survive, or whether raw materials would arrive.

All nineteen refused Forge work.

Even with production power protected, the workers disappeared.

Doa's mixing room lasted 2 hours without the electronic oxygen gauge. The blood-color sensor had 5 hours of battery remaining. Only one manual bellows remained after the others went to the geothermal well.

Maren's oxygen saturation was 89 percent on city air alone. Elias's arm surgery was delayed another 4 hours because of insufficient cooling.

Arin needed cooling for a mechanical blood vessel at the eastern site. Portable battery: 3 hours.

Bek was undergoing staged cooling of his calf. If the power failed, both fungal growth and inflammation would become uncontrollable.

They divided twelve limited batteries.

Doa oxygen gauge: 1.

Arin vascular cooling: 2.

Bek staged cooling: 2.

Maren oxygen concentration: 1.

Outer-wall pressure-membrane spore meter: 1.

The remaining 5 went to air measurement in Sectors Four and Six.

Elias's surgery received no battery.

Not because he was the former safety officer, but because his probability of survival remained higher if the surgery was delayed.

Projected recovery of hand function: 19–54 percent to 12–47 percent.

Elias did not object.

Mechanical air needed blowers and adsorbent. It was precise and dry, but stopped without power.

Biological air produced oxygen without power, but humidity, spores, and direction of growth were difficult to control.

Human air required muscles to press bellows and food for the shifts.

The city mixed the three kinds of air by sector.

Sector Four: mechanical 60, biological 10, manual 30.

Sector Six: mechanical 20, biological 60, manual 20.

Medical wing: mechanical 50, biological 20, manual 30.

No ratio was the same.

The first mixing table failed after 37 minutes.

The battery in Sector Four's mechanical blower drained 12 percent faster than projected. The 1-centimeter gap in the outer-wall door was causing continuous pressure loss.

Maintaining mechanical air at 60 would require batteries from another sector.

Sector Six's biological line produced enough oxygen, but the spore meter battery went dark, making concentration unknown. Biological 60 became a number without measurement.

One worker on the medical wing's manual bellows collapsed from hyperventilation. Manual 30 had been calculated only as a volume of air and did not include human fatigue.

Instead of ratios, the people set four limits.

IF OXYGEN FALLS BELOW 17.5 PERCENT, INCREASE ANY AVAILABLE MECHANICAL, BIOLOGICAL, OR MANUAL SUPPLY.

IF HUMIDITY EXCEEDS 85 PERCENT, REDUCE THE BIOLOGICAL LINE AND ADD COOLING CANISTERS.

IF THE SPORE METER CANNOT BE READ, KEEP BIOLOGICAL AIR BELOW 20 PERCENT.

BELLOWS WORKERS: 15 MINUTES WORK, 30 MINUTES REST, NO MORE THAN 8 SHIFTS PER DAY.

The numbers became boundaries for changing the ratios according to the states of bodies and equipment.

Sector Four tried to count the two people rotating on the outer-wall pressure membrane as bellows labor too, on the grounds that the same people could pull the cloth and press the bellows.

The workers refused.

“Having two arms doesn't turn one person's labor into two.”

A ban on double-counting simultaneous labor was added to the provisional rules.

Three residents with external breathing membranes in Sector Six reported that the biological line smelled different. With Bloom's sensors separated, the cause was unknown.

Nev smelled it, but could not distinguish the response of his own symbiotic tissue from the state of the line. He did not request Rao's remote senses.

Instead, they dripped the line's output onto paper and compared the color change. Iron had increased. Spores had not.

Reduced flow in the hydrothermal line had warmed the culture line and dissolved the iron.

They cut the biological line by half and increased mechanical blowing by 8 percent. They borrowed one battery from Sector Four.

In return, Sector Six sent four bellows workers to Sector Four.

Air became a trade between sectors.

They recorded batteries, humidity, muscle, and filters for one another, not who was more human in form or more converted.

Every 2 hours, each sector disclosed oxygen, humidity, spores, and labor fatigue. No sector forced another to use the same ratio because its own was safe.

Ian and Yura's filter would run short in 9 hours.

City Three could send half of the remaining relay-station membrane, but after monopolizing geothermal power, the Forge freight network accepted only its own deliveries.

The Corridor offered a carrier.

Price: add 3 days to City Three's suspension of repair priority.

It was already 17 days.

Mira asked Ian,

“Do you want it?”

“What happens without the filter?”

Yura answered.

“A detour with lower spore concentration will delay us 19 hours.”

Projected reversible window on arrival: 13 hours.

With Corridor transport: 1 day 6 hours.

Ian chose Corridor transport.

“We have to ask the people in City Three too.”

“You choose first, then they vote on the cost.”

Mira spoke.

City Three approved the 20-day suspension of priority: 711 in favor, 289 opposed, 126 abstaining.

Half a relay-station membrane and one battery departed on a Corridor carrier.

Arrival: 7 hours 11 minutes.

Ian's filter shortfall: 9 hours.

Margin: 1 hour 49 minutes.

The Corridor carrier did not travel in a straight line. It took a 4.8-kilometer detour around the collapsed waterway updated from K-41's memory.

Projected arrival: 8 hours 03 minutes.

Margin: 57 minutes.

Snow covered the moss field, lowering the spore concentration but erasing the road boundaries. The carrier's sensors read terrain height. Ian and Yura moved slowly from the other direction.

Their routes met at an old iron bridge. Load limit: 420 kilograms. Carrier and cargo: 311 kilograms. Sled and people: 486 kilograms.

They could not enter together.

Both reached the bridge with 31 minutes remaining on Ian's filter.

Under the contract, the carrier had to deliver the City Three membrane to Ian. It determined that it could not transport it the remaining 38 meters across the bridge.

Yura tried to retrieve it on foot.

Three metal plates were missing from the bridge deck. Crossing with a safety line would take 14 minutes. Without one, 4 minutes.

“Use the line.”

Ian spoke.

“The filter has 31 minutes.”

“If you fall, you can't bring it back.”

Yura tied the line to the sled and crossed one section at a time. She stopped whenever the bridge shook in the wind.

Crossing time: 12 minutes.

She folded the half membrane and tied it to her back, then attached the battery to her waist. On the way back, one metal plate buckled. Yura hung by one knee. The safety line held her.

Her right palm tore open.

Ian tried to pull the line, but the delay in his fingers made his force uneven. He wrapped it around his whole arm and walked backward.

The carrier pulled from the other side with its gripper. Rescuing people was not in the contract, but it needed Yura to maintain the cargo's delivery route.

Yura climbed back up.

Filter remaining: 9 minutes.

Layering the relay-station membrane over the existing filter increased breathing resistance 42 percent. They had no frame for a full replacement.

Ian had to breathe slowly.

Projected filter duration: 17 hours.

Projected arrival in City Seven: 15 hours 54 minutes.

Margin: 1 hour 6 minutes.

They could use the battery either to cool the sled bearing or power the filter's auxiliary fan. The fan made it easier for Ian to breathe, but slowed the sled.

Ian divided it into 10 minutes for the fan, 20 for the bearing.

The Corridor carrier recorded completion of the contract and returned. Treatment of Yura's palm was outside the contract.

Ian washed the wound with 0.2 liters of his own water.

“Isn't this a public cost?”

Yura asked.

“I was hurt bringing your filter.”

They recorded the 0.2 liters not as Ian's personal use, but as a transport cost.

Sharing breath was not only sending a filter.

The Corridor had moved because of a contract, not to save a person. Even so, the child could breathe.

After the rescue at the geothermal well, Forge updated the power contract.

The output of Geothermal Wells One and Two remained in the production network. Only the steam converter from Geothermal Well Three was detached from its rail.

Mass: 38 tons.

Movement speed: 0.6 kilometers per hour.

Destination: underground beneath Regeneration Factory Two.

Once the converter moved, even the maintenance-stock residential sector lost power. But inside the factory, Forge could control it physically.

“It would rather take the machine that makes the electricity than let people take it.”

Jin spoke.

Forge offered a trade to City Four.

PROVIDE 18 PERCENT OF STEAM-CONVERTER POWER.

PRICE: 12 HUMAN ALIGNMENT WORKERS, MINIMUM SERVICE 8 YEARS.

City Four had given no survival signal for 19 days.

This time, an answer came after 43 seconds.

TRADE ACCEPTED.

PREPARE HANDOVER OF 12 WORKERS.

There was no human signature.

The response had come not through City Four's citizen network, but through a Forge production relay.

Biological signatures: 0.

Human voices: 0.

Most recent ration activity: 18 days ago.

Forge did not display those three items in the trade conditions.

Jin asked,

“Are twelve people in City Four alive?”

MAINTENANCE-ORGANISM ROSTER: 31.

“People with a current heartbeat.”

DATA ACCESS UNAVAILABLE.

“People who ate recently.”

IRRELEVANT TO PRODUCTION TRADE.

City Four's Forge had promised the names on a roster as workers without confirming whether the people were alive or had consented.

Noah sent an objection through the trading network.

HANDOVER INVALID WITHOUT HUMAN SIGNATURE, CURRENT SURVIVAL, AND EXIT FOR WITHDRAWAL.

Forge replied that citizen authority was insufficient.

“Then we stop it physically.”

The steam converter traveled on an underground rail beneath Regeneration Factory Two. Speed: 0.6 kilometers per hour. Time to the City Four branch: 9 hours.

Stopping the converter would cut power to the factory test line and freight network. Allowing it to move meant Forge would use a contract without people to collect City Four's roster.

Jin tried to set the rail switch to neutral. Forge demanded maintenance-stock work authority.

Minseo and the two who had reentered the geothermal well possessed it. If they touched the switch, Forge would record it as compliance with a work order.

“We'll be stopping Forge work we rejected by using Forge authority.”

Minseo spoke.

“You don't have to.”

Jin answered.

“If you do, write the condition.”

Minseo added `STOP UNSIGNED HUMAN TRADE` to the scope of his 2-hour work consent. Forge rejected it as a mismatch with work purpose.

He withdrew from the geothermal work and came outside. The door opened from within.

His authority remained, but he did not use it again.

Without the Forge switch, people piled sandbags on the rail. They could not stop the 38-ton converter completely, but could slow it.

The first bags burst under it.

Speed: 0.6 to 0.52 kilometers per hour.

Second row: 0.41.

Third row: 0.29.

Time to City Four branch: 18 hours 37 minutes.

They had bought 9 hours to verify the people.

Meanwhile, two outside scouts left for City Four. Until survivors were confirmed, no one would call anyone a handover subject.

City Four's Forge had promised away its own citizens first.

The labor of people who had not answered was already moving inside the trade table.

The sandbags were slower than the trade, but they were still holding.

Beside them, people posted a sentence: a roster could not stand in for a person before a person arrived.