The first plank took his weight without complaint.
He had expected something. A groan, a flex, some physical acknowledgment that a person had stepped onto it. There was nothing. The wood was hard and cold through the thin soles of his shoes and it held him the same way the stone ledge had held him, without interest, without drama. He stood on it and waited a moment and then took another step.
Same. Solid.
He kept moving. Short steps at first, not from fear exactly but from caution. He did not yet know what the bridge would and would not hold. The planks were maybe twenty centimetres wide each, laid crosswise, the gaps between them narrow enough that he could not see through to the dark below unless he looked for it. He tried not to look for it. It was there regardless.
The bridge had a sound. That was the first thing that surprised him. In the cavern the silence had been total, but out on the structure there was a low constant hum, almost below hearing, that he felt more in his chest than his ears. Wind, maybe. The void below generating its own air movement as the temperature differentials did whatever they did in an enclosed space that deep. Or something else entirely. He did not know enough about the physics of bottomless pits to say.
He kept walking and let the hum be there.
Twenty metres in, he stopped and looked back.
The tunnel mouth was still visible, a dark rectangle in the cavern wall, the ledge in front of it, the sign post a thin vertical line beside it. The cave felt very far away already. He turned and looked forward. The bridge ran out ahead of him, the planks dark and even, the railings on each side casting faint shadows in the sourceless light. Fifty metres ahead, maybe sixty, the structure began to grey out and then was gone into the distance.
No end. Still no end.
He had known that from the ledge but knowing it from twenty metres out was different. From the ledge the bridge had been a thing he was looking at. Out here it was a thing he was on, a thing that was the only solid ground for as far as he could see in any direction, and the distinction mattered in a way he felt in his legs rather than his head.
He turned forward again. Kept walking.
The railing was to his left and right. He had decided early not to hold it. Partly because he did not trust it yet, had not tested the posts the way he had tested the planks, did not know how well they were anchored or how much weight they would take before they let go. Partly because holding it meant admitting he needed it, and he was not there yet. He walked in the middle of the bridge where the planks would be best supported, equidistant from both railings, and kept his arms at his sides.
The void was on both sides of him. He was aware of it the whole time, a peripheral fact, the dark dropping away two steps to his left and two steps to his right. He did not look at it. He looked at the planks directly ahead, picking his next three steps, moving through them, picking the next three.
'It was manageable.' That was the word he settled on. Not comfortable, not safe. Manageable.
He had gone perhaps sixty metres when he noticed the walls.
The cavern walls on either side of the bridge were not far. Ten metres from the railing, maybe twelve, close enough to see detail if the light had been better. He had registered them as background and moved on. But something made him look again now, something his eyes had caught without passing it to his brain yet.
The walls were not uniform.
There were holes in them. Small, circular, drilled or bored rather than broken, spaced at irregular intervals along the rock face. Some were at bridge height. Some higher. Some lower. He counted six on the left wall in the stretch he could see clearly, then stopped counting because counting was making him slow down and slowing down was not useful.
'Keep moving. Look, but keep moving.'
He looked at the holes on the right wall. Similar distribution. Similar size. He thought about what you put in a hole in a wall at bridge height over a bottomless drop, and he thought about it while he kept walking, and he did not come to a comfortable conclusion.
He moved to the centre of the bridge and stayed there.
The arrow came from the right wall without warning.
He heard it before he saw it, a sharp mechanical snap followed immediately by a hiss of displaced air, and he was already moving left before his eyes had registered what was happening. Not a decision. His body dropped into a half-crouch and lurched left and the arrow crossed the space where his right ear had been a fraction of a second before and buried itself in the left railing post with a sound like a short hard knock on wood.
He ended up on one knee, left hand on the planks, right hand out for balance. Two feet from the left railing. The void on the other side of it very close.
He stayed there.
His heart was loud. He was aware of it the way he was aware of the hum, a system running faster than it should. His breathing had changed too, gone shallow and quick. He stayed on one knee and breathed and did not move until the breathing had slowed to something he could work with.
The arrow was in the post. He could see it from here. Thin shaft, dark wood, the fletching grey-feathered and tight. The head was buried in the post but the shaft was long, longer than a hunting arrow, built for distance. It had come from the hole in the right wall, one of the holes he had been studying, and it had come fast and level and aimed at exactly the height a standing person's head would be at.
Not a warning shot. There was no such thing here. It had been aimed to kill and it had missed because he had moved and for no other reason.
He sat with that for a moment.
He stood up slowly, keeping his weight centred, and his left knee went soft.
Not injury. His leg just stopped holding for one step and he grabbed the railing with his right hand before he knew he had done it. He stood there with one hand on the post, weight against it, and waited for the leg to come back. It did. He straightened up.
He was holding the railing. He had decided not to hold the railing. He stood there with his hand on it for longer than he needed to, and when he finally let go his palm left a damp print on the wood.
He looked at it for a second. Then he looked at the right wall. The hole the arrow had come from was obvious now that he knew what he was looking for. Dark circle, forty centimetres across, set into the rock at exactly head height for a standing adult. He looked along the wall for the others. Found them. Then looked at the left wall and found those too.
The holes were not evenly spaced. He had thought they were irregular but he looked more carefully now and revised that. They were irregular at the large scale but locally paired, a hole on the left wall matched with a hole on the right wall at a similar height, staggered so that they did not fire at exactly the same depth of bridge. A person walking straight down the middle would pass through each pair in sequence, one shot from the left, then one from the right, then another from the left.
Or that was one reading. He could be wrong. He was working with limited information and a heart rate that had not fully settled.
He looked at the arrow in the post again. Then at the post itself, which had held. Then at the planks between him and the right railing. He needed to understand whether the trigger was pressure-based, motion-based, or on a timer. He had no way to test it cleanly without risking a second shot, and a second shot arriving while he was already studying the first would end things quickly.
'Move. Figure it out while you move.'
He started to stand, then stopped. The centre of the bridge was where he had been when the arrow fired. Maybe the paired holes were calibrated for centre. Maybe moving left was better. But the arrow had come from the right wall, which meant the hole on the right was the active one, which meant left was away from the source, which meant left was safer. Unless the left wall had a paired hole set to fire when something moved into its range from the right side. In which case moving left was exactly wrong.
He was still crouched. He had been crouched in the same spot for over a minute, which was longer than he had spent on his knee after the arrow hit him.
He stood up, moved to the centre, and started walking. The analysis had produced nothing useful.
He started walking again. Slower now, different. He stayed in the centre, watched both walls, and paid attention to the floor under his feet as well as what was ahead of him. The holes he could see were catalogued and left behind as he passed them. New ones appeared. He noted their height, their side, their rough position relative to his own.
Nothing fired.
That was interesting. He had passed three more holes on each side and nothing had come out of any of them. Either they were empty, or they were on a timer he had not yet understood, or the trigger was something specific to the spot where the first one had fired. He did not know which.
Three hypotheses. He could do something with that.
He picked the timer one first because it was the easiest to test. He stopped walking. Stood still in the centre of the bridge, watching the nearest hole on the left wall, and waited. Ten seconds. Twenty. Thirty. Nothing. He started walking again, then slowed almost to a stop, then walked at normal pace, varying it over the next twenty metres. Nothing fired at any speed.
That did not rule out a timer. It narrowed it. If it was a timer it was set to longer intervals than he had tested, which meant either it had already reset and he had walked past the trigger zone, or timing was not the mechanism.
He tried the second test at the next hole. He was approaching it from the left side of centre, about a metre off. Instead of continuing straight he shifted right as he drew level with it, crossing the centre line and moving toward the right railing slightly. He kept his pace steady. His shoulders pulled in without him asking them to. The hole passed on his left without firing.
He held what he had. Two tests, no shots. The trigger zone hypothesis was still alive. The first hole had fired when he was walking in a specific position, near the centre, maybe slightly right of it, and he had not repeated that position exactly since. The holes he had passed since the arrow were either empty or waiting for him to walk into the right spot.
Neither conclusion was comforting. He stored them both and kept moving, watched both walls, and paid attention to where his feet were on the bridge.
The arrow was behind him now, in the post, motionless. He did not look back at it.
He was eighty metres in. Give or take. The tunnel mouth was gone from sight behind him. There was nothing back there worth going back for.
He kept moving forward.
The walls had more holes ahead. He could see that much. He would deal with them when he reached them.