Brell blew one note on the whistle. The crew stopped where they stood.
The wall behind the chamber door moved inward again, slowly enough that Iven could follow the motion through the viewing panel. The padded blocks on Neri’s support compressed. The metal frame held, then eased back as the pressure passed.
“Everybody to the junction,” Brell said. “No running. Take the tools you can carry without slowing down.”
The workers obeyed. One reached for a heavy chest; Dessa stopped him and took the smaller case beside it instead. Neri checked the stair while Iven watched the support. Sera and Vela stood at the valve wheel. The pipe continued to carry heat at the reduced setting, its rhythm faster than the movement behind the wall.
The support flexed a third time. A bolt head turned a fraction in its bracket.
“Neri,” Iven said.
She came to the panel. “I see it.”
“Can we tighten it?”
“Not while the wall’s moving like that. If we trap the frame against it, the load goes into the next support.”
Brell checked the time on Elian’s copied sheet. “The intervals are getting shorter.”
Sera held her hand against the metal door. “The movement isn’t coming from the pipe.”
“I know,” Brell said. “What is it coming from?”
“I don’t know yet.”
A runner arrived from the upper control room with a folded message. Vela read it and swore under her breath.
“The regulator pressure has dropped,” she said. “They think the gauge failed.”
“Did they inspect the machine?” Iven asked.
“The message doesn’t say.”
“Then ask.”
Vela sent the runner back. He went up the stair two steps at a time. Brell kept her whistle in her hand and sent another worker to tell the workshops on the branch to prepare for a shutdown.
The city above them continued its ordinary work. Iven could hear a cart crossing a deck joint, its wheels rattling in a familiar sequence. Someone called for a delivery outside the service stair. The sounds made the movement beneath the wall feel less urgent until the support flexed again and the bolt turned another fraction.
“Shut the branch,” Brell said.
Vela put both hands on the valve wheel. Iven joined her. Together they turned it until the heat flow stopped. The pipe’s hum faded, but the slower movement continued.
“That will cost the workshops heat,” Vela said.
“I know.” Brell handed her the key. “Tell them I ordered it.”
“You don’t have to take it alone.”
“Then put both names on the note.”
Iven admired that more than he said. People often spoke about responsibility as if it were a weight one person had to carry to prove strength. Brell and Vela were making sure the people affected could see who had made the decision and why.
Kesh arrived from the neighboring line with a report of creatures moving through two service passages. They had not attacked anyone. One crew had closed a door; another had withdrawn from a pipe trench after hearing scraping beneath the floor.
“Are they heading toward this chamber?” Neri asked.
“I can’t tell. The passages connect in more places than the map shows.”
Elian had gone to the survey office with the ledger copies. He returned now carrying a revised plan of the regulator gallery and a note from the archive clerk. The diagram volume existed, but the office had not approved a second consultation.
“That may no longer matter,” Sera said.
“It matters if the diagram tells us what the regulator controls.”
“Can you reach the upper control room?” Iven asked.
“I can ask for access.”
“Ask quickly.”
Elian went with Vela. Sera stayed at the chamber, measuring the intervals between movements. Kesh positioned herself at the junction where she could watch both the low passage and the stair. Neri sent Dessa and Jem to inspect the occupied deck above the heat line. Iven carried a coil of rope to the nearest door and tied it along the handrail, leaving a clear guide for anyone who had to move through the passage in poor light.
The runner returned without Elian or Vela. His face was flushed.
“The control room says the regulator is being inspected,” he said. “They won’t let anyone down to the gallery.”
“Harl is down there,” Iven said.
“I didn’t see him.”
Sera looked at the time. “If the pressure dropped because a line opened, the tissue draw may have changed. If it dropped because the gauge failed, the machine could still be under load.”
“Two bad possibilities,” Brell said.
“More than two. Those are the ones we can name.”
A deep vibration passed through the floor. The lamps swayed. One of the workers at the junction caught a hanging tool before it fell.
Kesh stepped toward the low passage. “Something’s moving in there.”
A pale head appeared at the far end, followed by another. The creatures did not charge. They crossed the opening one after the other, moving toward the heat chamber. Kesh held up her hand. Brell’s crew retreated to the stair.
The first creature reached the closed door and struck it. The second climbed the wall beside it. Iven seated plate brace, spring step, and piston strike, but he did not advance. The door was sound. The workers were clear. Fighting the creatures in a narrow passage would add danger without protecting anyone.
The door shuddered under a second blow. A hinge bolt dropped to the floor.
“That hinge won’t hold,” Neri said.
Brell looked at the stair. “Everyone up.”
Iven stayed with Neri long enough to move the tool cart out of the way. They pushed it into a side recess, leaving the main passage clear. The creatures struck the door again. The upper hinge bent.
Kesh backed up the stair, shield raised. “They’re not following the crew. They’re going for the chamber.”
“Which is where we’re standing,” Iven said.
“Not for long.”
The upper hinge tore free. The door swung inward against the remaining hinge. One creature squeezed through. The other followed, scraping its armor against the frame.
Iven and Neri reached the stair. Brell blew two notes. The crew climbed to the occupied deck, where the light was brighter and the air carried the smell of cooking rather than hot oil. A cluster of workers had gathered beside the service hatch. Dessa and Jem were among them, holding a rope barrier across the entrance.
“The support posts above the line are sound,” Neri said. “For now.”
“For now” became less reassuring each time anyone said it.
A message arrived from Tavin. Cage Seven was positioned at the local transfer landing with its passenger space clear. He could move injured workers to the clinic or take people across a damaged section if needed. He could not clear the entire district with one cage, and his note did not pretend otherwise.
Iven went to the landing to help check the route. The cage rested in its frame, its gate open. Tavin had two crew members testing the brake and the guide wheels. A woman with a bandaged ankle sat on a bench nearby, waiting for a routine transfer. Tavin spoke to her quietly and arranged another cage before moving the bench out of the way.
“You’re planning for an emergency,” Iven said.
“I’m planning for a delay. Emergencies get offended if you name them too early.”
“Does that work?”
“No. But it makes the passengers less nervous.”
They checked the landing rail and the short bridge to the adjoining deck. Neri’s crew had reinforced the bridge after the Lower Return failure. It flexed under load but returned to position. Iven tested the handline and replaced a frayed tie with a length of ordinary rope.
Elian reached them as they finished. His coat was dusty, and he carried a folded instruction bearing a control-room seal.
“They’re shutting down one regulator cylinder,” he said. “Harl found a leak in the return line.”
“Is he safe?” Iven asked.
“He was when I saw him. The crew is withdrawing after the shutdown.”
“Why only one cylinder?”
“The control room says shutting the whole system at once could destabilize the upper lines.”
Sera arrived behind him. “They may be right about that. We don’t know what the system is suppressing, or what happens when it loses pressure.”
Tavin looked from one to the other. “Can you tell me what to move first?”
“Keep the landing clear,” Iven said. “If the lower line fails, workers may need to come up here. Don’t bring passengers into the chamber route.”
Tavin nodded and sent one of his crew to the lower gate. The instruction was specific enough to use. It did not promise that every possible failure had been anticipated.
A metallic report echoed from beneath the deck. The landing rail shook. The woman with the bandaged ankle caught the edge of her bench.
“That’s not a delay,” she said.
“No,” Tavin replied. “It’s not.”
Another report followed, then a low sound that Iven felt more than heard. The deck rose beneath his boots. It did not rise like a lift. It tilted, held, and settled in a direction that made the hanging lamps swing across the landing.
The people on the bench stood. A cart rolled against its brake. One of Tavin’s crew caught it before it struck the rail.
Iven looked toward the rear of the saddle. Buildings beyond the landing shifted against one another, their flexible joints opening wider than he had ever seen. A row of hanging sheets snapped in the air. Somewhere farther down the lane, glass broke.
The deck settled again.
Sera gripped the rail. “That wasn’t the regulator.”
“No,” Elian said. “It wasn’t.”
A bell began to ring in Rung Ward. Another answered from the next deck. The signals were uneven, sent by people using whatever they could reach.
Tavin closed Cage Seven’s gate. “I’m taking the injured woman to the clinic. Then I’m coming back.”
Neri reached the landing with Dessa and Jem. “The support posts above Brell’s chamber moved,” she said. “We cleared the work area. The lower passage is empty as far as we know.”
“Brell?” Iven asked.
“Coming up with Kesh.”
The deck tilted again, less sharply this time. A crack ran across the plaster of the wall beside the landing. Dust fell onto Neri’s shoulder.
Iven took out his hammer. “Where are your crews?”
“Split between the heat line and the rope-shop lane.”
“Can they reach each other?”
“By the upper bridge. If it holds.”
“Then we check it.”
They moved before the next tilt. At the bridge, one of the flexible joints had opened farther than its retaining pin allowed. The pin was bent but still seated. People were crossing in both directions, some carrying tools, others carrying children.
Neri stopped them at the near end. “One at a time until we brace it.”
A man carrying a sack objected. “I’ve got to get home.”
“So does everyone behind you,” she said. “If you load the joint all at once, none of you will.”
He looked at the opened joint and stepped aside.
Iven seated clamp bridge and plate brace. He set the clamp against the sound side of the joint while Neri and Jem fitted a temporary timber beneath the rail. The graft held the metal long enough for them to drive a wedge into place. Iven released the clamp and tested the joint with his own weight. It moved, but the timber carried the rail.
“One at a time,” Neri repeated.
The first woman crossed with a child in her arms. The bridge dipped and held. A second followed. Iven stayed beside the joint, ready to catch it if the pin slipped.
Brell came up the lane with Kesh and the last of the heat crew. She had a cut across her forehead where a falling tool had struck her, but she was walking. Behind them, a low plume of dust rose from the service stair.
“The chamber door’s gone,” she said. “The creatures went inside. We closed the upper hatch.”
“Anyone left below?”
“No.”
The deck gave a third, deeper shift. This time the bridge joint opened against the timber. The temporary brace groaned. Iven set his shoulder against the rail and formed a plate brace across the contact, spreading the pressure while Neri drove another wedge.
The people waiting at the far end froze.
“Keep moving,” Neri called. “One at a time.”
They did. A man with a sack. A girl carrying a cage of birds. Two workers supporting someone whose ankle had turned. The bridge moved beneath each of them, but the brace held.
Iven’s left forearm warmed. He kept the force small and steady, using the timber to carry most of the load. The graft could help a structure survive a moment. It could not replace the structure for the rest of the day.
When the last person crossed, Neri tied a rope across the bridge entrance. “Closed until we inspect the far support.”
A bell rang again from Rung Ward. This time the signal was longer, urgent enough that people on the lane stopped to listen.
The ground beyond the saddle seemed to shift sideways. Iven realized the city had not merely tilted. Mercy was turning.