The first bone was wedged in the fan blades.
Iven found it by lamplight while Lenn held the housing steady. It was narrow and hollow, with a joint at one end and a row of shallow scratches along the shaft. Not human. The blade had bent around it and stopped, leaving the lower passage without the air it was supposed to carry.
“Bird?” Lenn asked.
“Probably.”
“Probably isn’t good enough for the people working below.”
“No. It’s good enough to know something got into the vent.”
Kesh crouched beside them. She took the bone with padded tongs and laid it on a clean cloth. The scratches crossed one another at irregular angles. A few gray fibers clung to the joint.
“Kite,” she said. “Young, judging by the size. Those aren’t beak marks.”
Lenn looked toward the passage. “Another kite?”
“Could be teeth. Could be a tool. I won’t know from one bone.”
The maintenance hatch opened onto a sloping tunnel beneath the station. Its walls were a mixture of metal ducting and Mercy’s mineral armor. Pipes crossed the ceiling, carrying warm air toward the drying rooms. The air current had slowed when the fan stopped. Workers had been using the long route since yesterday, but three people remained at a lower junction, closing valves before they could leave.
They were due back an hour ago.
Neri checked the hatch’s outer frame. “The station can hold if we keep the door open. I want a line on the lower landing before anyone comes out.”
Rysa’s crew fixed a rope to the station bracket and ran it through the hatch. Kesh took her hooked pole. Iven checked his spanner, the one recovered from the kite’s nest, and seated plate brace, piston strike, and hook cast. He kept winch and bell ready in the library, but three channels were all he could carry into the passage at once.
Sera had gone to the lower junction by the alternate route. She was not expected to reach it for another forty minutes. Iven did not intend to wait if the workers had a problem he could solve now.
“Two people go in,” Kesh said. “One stays at the hatch with the line. If we find the crew, we get them out. If we find what’s taking the birds, we don’t chase it into a place we can’t leave.”
“That’s a good rule,” Iven said.
“I’m glad you like it.”
“Does it still apply if it chases us?”
“Especially then.”
They entered with lamps covered by wire guards. The tunnel narrowed after the first bend. The metal ducting ended, and the walls became pale, ridged material that felt warm through Iven’s glove. Water ran in a shallow channel along the left side. A torn strip of cloth hung from a bolt above it.
Kesh examined the cloth. “Work apron.”
“From the missing crew?”
“Maybe. It’s fresh.”
Iven heard the scraping before he saw the next bend. It came in short bursts, followed by a wet click. He lifted the lamp. The light reached a low arch and stopped against a heap of pale objects on the floor.
Bones. Not a whole skeleton, but pieces gathered together: thin bird limbs, two larger rib-like fragments, and a curved plate that might have come from one of the pale creatures inside Mercy. The pile had been dragged against the wall, leaving streaks in the damp surface.
Kesh stopped beside him. “This isn’t a guardian nest I’ve seen.”
“What have you seen?”
“Guardians don’t usually carry prey into a pile. They may strike people, but they leave the bodies where they fall.”
The clicking stopped.
Iven put his back toward the tunnel wall. The arch ahead was too low for a person to pass without crouching. Above it ran a metal duct with a broken seam. The seam moved, opening a fraction and closing again.
“Something’s in there,” he said.
Kesh lifted her pole. “Back to the bend.”
A voice came from beyond the arch. “Please don’t leave.”
Iven lowered the lamp. A hand appeared in the gap between the bone pile and the wall. Its fingers were wrapped in cloth. A man crawled into view, dragging one leg. His coat bore the mark of the lower vent crew.
“The others?” Kesh asked.
“Across the chamber. The bridge dropped.” He pointed beyond the arch. “One fell. The other went down after him.”
“What happened to you?”
The man looked at the duct. “It came out when we opened the valve. It took the lamp. We ran.”
Iven moved toward him. Kesh caught his sleeve.
“Watch the seam.”
The man tried to pull himself farther into the tunnel. His leg left a dark smear. Iven could see a deep cut through the cloth above his knee.
“What’s your name?”
“Bram.”
“Bram, keep coming. We’ll meet you halfway.”
The seam burst open.
The creature unfolded from the duct like a length of rope thrown into the air. Its body was low and jointed, covered in dark plates that reflected the lamp in narrow strips. Six limbs gripped the ceiling. Two longer forelimbs ended in curved hooks. Its head was almost flat, with no visible eyes, and a ring of short feelers moved around its mouth.
It struck Bram before Iven could reach him.
Iven drove the plate brace between the creature’s descending limb and the worker. The hook hit the brace hard enough to send pain through his shoulder. He turned the force aside, grabbed Bram’s coat, and pulled him backward. Kesh hooked the creature’s other limb and dragged it toward the wall.
The animal released the ceiling and dropped. It landed on the bone pile with a sound like stones falling into a basin. Kesh’s pole caught beneath one of its plates. She pulled free before it could drag her closer.
Bram crawled behind Iven. The creature’s feelers touched the floor, then lifted toward the lamp.
“It follows the heat,” Kesh said.
“You know that?”
“I know it turned toward the lamp. Move it.”
Iven threw the lamp past the creature. It struck the wall beyond the arch and rolled, its guarded flame still burning. The animal turned toward it, body flexing. Iven used the opening to push Bram toward Kesh.
“Get him to the hatch.”
“The others are ahead.”
“I’ll get them.”
Kesh looked at the creature, then at the arch. “Don’t go through while it’s between you and the exit.”
“I won’t.”
The creature reached the lamp. Its hooked limb struck the guard, denting the wire. Iven cast his hook toward the metal duct above it. The tether caught on a sound bracket. He pulled himself forward and upward, using the anchor to shift his weight over the animal’s back. As he passed, he drove a piston strike into the joint where its forelimb met the body.
The blow cracked a plate. The creature twisted, its hook cutting through the air where his leg had been. Iven landed beyond it and released the tether. He had placed the animal between himself and the hatch for a moment, but it was also between him and the open chamber. He needed to move it again before it could turn.
He caught the damaged duct with his right hand and hauled it down. The loose sheet of metal fell across the creature’s back. It snapped at the moving edge. Iven struck the duct with his spanner, producing a sharp clang, then stepped through the arch while the animal was occupied.
The chamber beyond was larger than he expected. A narrow maintenance bridge crossed a deep channel filled with slow-moving dark water. The bridge’s near end had collapsed, leaving a gap of several meters between Iven and the remaining span. On the far side, a woman held a rope tied around a fallen worker’s chest. The worker hung below the bridge, one hand gripping a crossbar.
“Can you pull him up?” Iven shouted.
“Not alone.”
“Hold him where he is.”
He cast the hook toward a thick beam above the far end of the gap. It caught on the second attempt. He tested the line with a short pull. The beam held. He could swing across, but the creature was already scraping beneath the fallen duct behind him.
He crossed anyway.
The hook line carried him over the gap. His boots struck the far side of the bridge, and he dropped to one knee to absorb the landing. The woman stared at him.
“You came through that?”
“I was told there were two people here.”
She handed him the rope. Together they hauled the fallen worker up until he could get an elbow over the edge. He was conscious, bleeding from a cut on his scalp, and furious about the blood getting into his eyes.
“Can you stand?” Iven asked.
“Give me a moment.”
The creature struck the duct again. Metal bent. Iven saw one hooked limb appear through the arch.
The woman followed his gaze. “Can it cross?”
“I’m about to find out.”
He examined the bridge. The remaining span was fixed to the far wall with two brackets. A heavy pipe ran above it, supported by a chain. The chain had enough slack that the pipe could be lowered a short distance if the retaining pin came out.
He did not have a winch seated. He had plate, piston, and hook. The creature’s limb found the near edge of the gap and gripped it. The animal pulled its body through, plates scraping against the arch.
“Move behind the pipe,” Iven told the workers. “Stay low.”
The woman helped the injured man toward the wall. Iven climbed onto the bridge rail and reached for the chain’s retaining pin. It was secured by a wire loop. He pulled the wire free with his awl and caught the pin in his right hand.
The creature looked toward the movement. Its feelers spread. It crossed the gap by climbing along the underside of the duct, hooks finding the seam.
Iven struck the pin with his hammer. It moved but did not come out. The creature released one limb and swung closer.
He put a piston strike through the hammer head. The pin shot from its socket. The chain ran through the support ring, and the pipe dropped until the remaining length caught it. It struck the bridge between Iven and the creature, shaking the entire span.
The animal fell onto the pipe rather than into the channel. Its hooks gripped the metal. It climbed toward him, using the pipe as a direct route.
“That didn’t work,” the woman said.
“It changed the direction.”
Iven jumped down from the rail and moved toward the creature. He raised the brace to catch its first hooked strike, then stepped inside the arc of the second. His spanner hit the cracked joint he had made near the arch. The plate broke farther, exposing dark tissue beneath.
The creature recoiled. Iven followed, keeping it on the pipe where its longer limbs had less room to spread. It lunged again. He caught one hook against the brace, pushed it outward, and drove a piston strike into the exposed joint.
The impact knocked the limb loose from the pipe. The animal twisted, caught itself with two smaller feet, and swung its head toward his arm. The feelers touched his sleeve. Its mouth opened.
Iven did not pull back. He seized the pipe with his right hand and used the hook cast at close range to secure the creature’s remaining forelimb to a bracket. The tether held for only a few seconds, but it stopped the hook from reaching him. He stepped to the side and struck the exposed joint again, this time with the hammer and a concentrated piston impulse behind it.
The limb failed. The creature lost its hold on the pipe and fell into the dark water.
It struck the surface with a heavy splash. The current turned the animal once against the far ledge. Its hooked limbs did not move again, and its broken head remained above the water until the current carried the body beneath the bridge.
“Is it dead?” the injured worker asked.
“It struck the ledge. I saw it stop moving.”
“Can it climb back?”
“Not this one. We don’t know if there are others.”
Iven cut the hook tether loose and helped the workers toward the far stair. The woman led, knowing the route to the lower junction. The injured man walked with one arm across Iven’s shoulders. They reached a locked gate and found the key hanging on a cord beside it. Iven opened the gate, then closed it behind them without locking it.
Sera met them at the junction with two stretcher bearers. She took one look at the man’s head and directed him onto the canvas. The woman told her about Bram and the creature. Sera sent one bearer toward the upper hatch, where Kesh and the station crew could bring Bram down by the shorter route.
“You fought it alone?” Sera asked.
“It wasn’t interested in a discussion.”
“Are you hurt?”
“Shoulder and pride. The pipe didn’t stop it.”
She checked his arm anyway. The graft was warm, his shoulder bruised beneath the coat, but nothing had opened or gone numb. The return circuit had stayed quiet through the blows. He still had enough charge to use the brace again if the animal appeared.
Kesh arrived with Bram a few minutes later. The worker’s leg had been bandaged, and he was awake enough to complain about the stretcher’s smell. Kesh listened while Iven described the creature.
“Dark plates, six support limbs, two hooks,” she said. “I haven’t seen one inside Mercy before.”
“Could it be a guardian?”
“It carried bones into a pile and took a lamp. I think it may be a predator using the vent, but I want to see the remains before I name it.”
“You can see them when we have a safer way in.”
She nodded. “Did it survive the water?”
“No. I saw it strike the ledge and stop moving.”
Bram reached into his coat and produced a small brass plate on a cord. “Found this near the old valve,” he said. “Before it came out.”
The plate carried a worn diagram: a fan, a set of branching lines, and a symbol Iven recognized from Elian’s older map. It was a movement mark, the sort that had once told workers to measure a living surface before drilling.
“Where was it fixed?” Iven asked.
“On the wall behind the valve. There were more marks underneath, but the lamp went out before I could read them.”
Iven turned the plate over. On the back, a row of tiny holes formed a pattern that might have held a second plate in place. Whatever had been attached there was gone.
The injured man on the stretcher raised his head. “The fan below the chamber feeds the old passage. If it stops, the drying rooms lose air.”
Lenn had been right to keep workers out. Now they knew why the passage was dangerous, and they knew there was a fan worth recovering. Iven looked at the brass plate, then at Kesh.
“We need a way back in.”
“A safer one,” she said.
He agreed. The next visit would not be a chase through a duct with a predator at his back. He had defeated the thing in the chamber and brought both workers out, but others might be hiding farther along the dark water. He wanted any next encounter on ground he had chosen.