The double horizontal mark. Fifth time.
He had come to read this mark as a different category of chest entirely. Not safe versus trap, the binary the single line managed. Something more like: pay attention, this changes something. The vine arm. The scooter. The hydraulic arm. The HUD helmet. Each one had changed what was possible in a way the food and water chests did not. He checked the floor and the lid and the latch housing and opened it.
Two pieces, identical, each one a leg assembly from mid-thigh to ankle, the actuator housings running along the outer surface in a line of ridged segments. Two coiled cables in a separate pocket of the chest, both with the same connector at each end, one fitting matching the torso's lower ports and the other matching a socket at the top of each leg piece. He had noticed the torso's lower ports when he fitted it and had not known what they were for, the same way he had not known what the lower torso ports were for before the leg armour connected them. He sat on the planks and fitted the right leg piece first. The segments clicked on from thigh to ankle, each one locking before the next, the fit snug over the tracksuit fabric. The left leg, the same. Neither leg was injured. The fitting took thirty minutes and required no bracing against the scooter, no twelve-minute struggle, no vine arm holding panels in place. He was getting faster at this.
He connected the distribution cables: torso to right thigh, torso to left thigh. The HUD's left panel updated as each connection completed, new indicators appearing below the steam core pressure gauge. Leg actuator load: zero. Stride force multiplier: one point zero. A gait analysis bar he did not yet have a reference for. He stood up.
He walked first.
The difference arrived immediately, not dramatically but specifically. The push-off from the rear foot was more efficient, each stride's force amplified through the actuators so that the same muscular effort covered more ground. The landing absorbed differently, the hydraulic segments taking the impact that would otherwise travel up through his knees and hips. He had been managing impact fatigue across three weeks of bridge and had stopped noticing it the way he had stopped noticing the cold before the torso. He noticed its absence now.
He walked to the end of the stable section and back. The HUD showed the stride force multiplier at one point four. He had been walking at roughly forty percent more efficiency than his legs alone provided and had not felt the extra effort.
He jogged.
The suit absorbed the increased impact load without changing its character. His breathing rose to match the pace. His legs did not. The actuators handled the cycling load of the jog, the push and the land and the push again, and his muscles were managing the motion rather than the weight of it. He had not jogged since before the cave. He had not jogged on this bridge at all. The bridge was not designed for jogging and neither was he, but the legs were making it possible.
He stopped at the end of the section and looked at the next stretch. The HUD thermal showed no cold floor signatures. Post spacing normal. He made a decision.
He ran.
The suit changed running entirely.
His body's contribution was the motion and the direction and the reading of the bridge ahead. The legs managed the rest. Stride force at one point eight. Actuator load in the yellow band but not the red. His heart rate climbing in the upper left display, his breath coming faster, the bridge moving under him at a pace that no section of it had moved at before. The railing posts blurred. The walls slid past. The grey ahead contracted faster than it ever had on the scooter.
He had been running for perhaps forty seconds when the first plank dropped behind him.
He heard it: the mechanical snap of a release, the brief rattle of the panel going, and then nothing, the void absorbing the sound before any echo could return. He did not stop. He looked back over his right shoulder without breaking stride.
The section was dropping in sequence.
Each plank or panel releasing a fraction of a second after the previous, the collapse advancing forward through the bridge at roughly the pace of a walking person. He had already passed the trigger zone, his speed had put him two or three metres ahead of it when it fired, and the collapse was now chasing the position he had been rather than the position he was. The gap between him and the leading edge of the fall was narrow. Narrow enough that if he slowed it would close.
He ran.
Behind him the bridge was going into the void in sequence, plank by plank, panel by panel, the collapse methodical and unhurried, designed for a walking pace that he was no longer walking at. The scooter was back there. He had left it at the edge of the stable section when he started the run. He heard the plank it was parked on drop at roughly the twenty-second mark of the collapse, a slightly heavier sound than the others, and then the scooter was gone and he did not look back a second time.
He ran.
The HUD showed heart rate at one hundred and seventy-two. Actuator load in the high yellow. Stride force two point one. He could feel the steam core's warmth through the torso plate, hotter than usual under load. The vine arm was extended slightly for balance, its tip skimming the air beside him. The hydraulic arm swung with each stride, its weight adding to the rhythm rather than fighting it. The pistol stayed at his hip.
He had no idea how long the collapsing section ran. He could not see the end from in front and he was not going to stop to measure it from behind. He ran and read the bridge ahead and ran and the bridge kept giving him planks and he kept putting his feet on them and the collapse kept following at its fixed, unhurried, lethal walking pace.
One hundred and sixty metres. One hundred and eighty. He was estimating from the wall marks falling away on his left, two of them passing in what felt like seconds. The collapse was still audible behind him, still sequential, still unhurried.
Then it stopped.
Not gradually. One drop and then silence, the bridge behind him suddenly quiet after the sustained percussion of the collapse. He ran another fifty metres before he let himself slow, the legs absorbing the deceleration, and then he stopped and turned around.
The gap stretched back two hundred metres, perhaps slightly more. Where the bridge had been there was now void, the planks gone, the crossbeams below them visible from above as a series of bare struts across the open drop. The railing posts on each side stood intact, the rails still running between them over nothing, a frame without a floor.
The scooter was gone. Everything in its storage slot with it. The bolt, the wood fragment, the hinges he had removed from the high-quality chest. Three weeks of small accumulations, built up item by item, now in the void with everything else the bridge had taken.
He noted this. The items were gone. He adjusted his mental inventory: no scooter, no storage contents. He had the suit, the pistol, the watch, his food and water in the jacket pockets. That was what he had. The bridge had taken the rest and the bridge did not offer refunds.
He looked at his legs. The HUD showed actuator load returning to baseline, stride force back to one point four at standing rest. His breathing had normalised. His muscles had not delivered a sprint. The suit had delivered a sprint and his muscles had directed it. There was a difference, and he felt it in the absence of the exhaustion that two hundred metres at that pace should have produced.
The trap had been designed for walkers. A walker would have been consumed by the sequential collapse in the first twenty metres. He had run faster than the collapse's advance rate because the leg armour had made running sustainable. The suit had earned its place three times over in the span of two minutes.
He turned and walked forward.
No scooter. The legs were faster than the scooter had been over short distances, and over long distances the legs would not run out of fuel in the way the scooter had. The tradeoff was not identical, the scooter had carried things, given him a storage slot, changed the bridge's texture in ways he would miss. But he was moving and the bridge was in front of him and there was no useful comparison to make between what he had lost and what he was walking on.
He kept going. The legs carried him forward at one point four times the efficiency of his own body alone, and the bridge had more of itself ahead, and somewhere further along it there was an end.