The temperature dropped a degree more before anything else changed. Then the air thinned — same filtered sweetness as before, but stretched, edged with the dry taste of spent current. Something had discharged in this corridor recently. The system hadn't ventilated it. Maybe it wanted them to notice. Maybe it didn't care either way.

  Their footsteps didn't echo.

  They registered.

  Jake went lower without slowing — his head dropping, ears tracking the walls in small precise movements. His tail held steady at half-mast. Working. Griff had been watching that tail for years and knew the difference between cautious and afraid; this was cautious, which meant the room was worth thinking about but hadn't declared itself yet.

  The corridor curved right. No branch. No decision offered. A sentence with only one word in it.

  "Don't love a corridor with no exits," Scarab said.

  "None of them have exits," Kyle said.

  "I know. I hate each one individually."

  Then the floor changed.

  Not texture. The tone of it — a low vibration that rose through composite into bone, the kind that settles in the back teeth before the brain assigns it a category. Subtle. Patient. Present in a way that suggested it had been there for some time and had simply been waiting for them to be still enough to feel it.

  Jake stopped. His whole body went to attention.

  Griff's fist came up. The formation locked.

  Valley crouched and pressed his palm flat to the floor. He was quiet for a moment. His jaw tightened.

  "It's mapping cadence," he said. "Reading our rhythm. How we walk."

  The silver thread beneath Don's bandage gave a quiet pulse — a nudge more than a flare. He looked down at it.

  "It's not just mapping," he said.

  The thrum deepened almost imperceptibly, aligning — settling into the interval between their steps like it had always lived there and they'd only just arrived to complete it.

  Jake barked. Sharp, clean, perfectly placed.

  The vibration skipped. Recovered.

  "What did that do?" Archie asked.

  "Interrupted it," Valley said.

  "For how long?"

  "About half a second."

  "Is half a second—"

  "Half a second is everything," Kyle said. He was watching the walls with the focused attention of someone building a file. "Systems run on certainty. Break the certainty and you change what they can predict. Half a second of noise means the model has to recalculate from a degraded baseline."

  Scarab considered this. Looked at Jake. "So the plan is we all bark."

  "The plan," Griff said, "is we stay off the rhythm. Move when it doesn't expect us to move. Make every step cost it something."

  "I can do that," Mad said. "I have never in my life moved at a predictable tempo."

  "That is genuinely the most useful thing you've said this week," Elin told him.

  "I contain multitudes," Mad said. "Largely useless. Occasionally vital."

  Griff looked at Don. The thread was pulsing in a slow, interested rhythm — not pain, not flaring, but present. Conversational.

  "Tell me if it sharpens," Griff said.

  "You'll see it in my feet before I can tell you."

  "Then I'll watch your feet."

  They moved wrong — deliberately, irritatingly wrong. Two short steps, a drag, one long stride, a pause. No pattern. No comfort. The formation shuffled through the corridor like a crew that had collectively forgotten how walking was supposed to work, which was more or less the point.

  Mad, moving last, said: "I feel ridiculous."

  "You look normal," Archie said.

  "That's the worst thing you've ever said to me."

  The corridor opened into the chamber without transition — the walls simply stepped back and the ceiling lifted and the thing that had been a vibration became a pulse with geometry, something structural, something that breathed.

  Unauthorized reproduction: this story has been taken without approval. Report sightings.

  Circular. Domed ceiling that caught the pulse and layered it back from three angles at once, so the sound arrived in a slight offset that made the inner ear work. Walls brightening and dimming on the beat. Not alarming. Building.

  Valley had the rig up before anyone asked.

  "Timing field," he said. "Entrainment architecture. It generates a rhythm and waits for biology to sync to it — heart rate, breathing, movement. The longer you're inside it, the harder it gets to run at a different tempo."

  "How long before it works?" Scarab asked.

  "Depends. Fear helps it."

  "Fantastic," Mad said. "And fatigue?"

  A pause.

  "Fatigue helps it more."

  Mad closed his eyes for a beat. Opened them. "Right. So we're walking into a room specifically designed to exploit the fact that we're tired and scared, that will try to turn us into metronomes, and our strategy involves a middle-aged dog doing counterpoint."

  "He's not middle-aged," Archie said.

  "He is in human years."

  "That's a different calculation—"

  "Archie."

  "Yes?"

  "I know how dog years work."

  Jake, from the centre of the chamber, looked at Mad. Then barked — sharp, perfectly timed in the gap between two pulses. The rhythm stuttered. Light flickered. The field lost half a second, found itself, rebuilt.

  Mad watched it.

  "Fine," he said. "Fine. The dog is doing counterpoint. I've had worse plans."

  Don had gone still. His breathing was deliberately uneven — he'd been practising the irregularity since the salvage bay — but the bandage at his stump had begun to glow faintly, silver pulsing in time with the chamber, and his good hand had moved to cover it without him appearing to notice.

  "Don," Griff said.

  "I know." Don's jaw was set. "It's coherent. It wants to complete something. The thread — it feels like a question the room is answering." He pulled his hand away from the bandage and pressed it flat against his thigh instead — a deliberate act, visible in the effort it cost. "I'm staying off it."

  "Tell me when that gets harder."

  "You'll know."

  "Valley," Griff said.

  "Counter-frequency." Valley was already positioning, the rig warm in his palm, the new filament wrap tight at his wrist. "I can collapse the peak. But the timing has to be exact — I need a signal."

  He looked at Jake.

  Jake looked back at him — the long, level look that Valley always held a beat too long, something in his expression that he couldn't quite name and never tried to.

  "On your mark," Valley said. "He needs to bark at the same moment."

  Griff crouched in front of Jake.

  "Jake."

  Jake's ears came forward.

  "On Valley's mark."

  Jake sat. He knew how to wait.

  The chamber built — pulse deepening, the membrane at the far wall brightening toward white, a seam forming through its centre like a split decision. Don covered the bandage again, jaw tight, the pressure of palm against stump a visible refusal. Mad shifted his weight deliberately off-beat. Elin moved her knife hand to a loose grip and back, purely to stay arrhythmic. Kyle counted intervals under his breath. Archie, on pure instinct, quietly listed two things that were still working.

  Valley's hand dropped.

  The rig screamed.

  Jake barked.

  The pulse collapsed sideways — light fracturing across the dome, the membrane catching mid-breath, its seam cracking wide, its centre blazing erratically for one bright second.

  "Now," Griff said.

  Jake went first. Elin on his heels. Scarab and Valley through together, the rig still spiking interference behind them. Mad put a hand briefly on Archie's shoulder and they crossed as one. Kyle went without looking back.

  Don crossed last.

  His step landed in the gap between two struggling pulses, the chamber fighting itself, the thread pulling toward something that couldn't quite resolve what it was asking. He was through before it found the question.

  The membrane sealed.

  The silence that followed had a specific quality — not the absence of sound but the absence of a process. Whatever the room had been building stopped building it.

  Everyone stood for a moment and breathed.

  Scarab was the first to speak.

  "The dog coordinated that."

  "The dog coordinated that," Elin confirmed.

  Scarab looked at Jake, who was already walking forward with the unhurried certainty of an animal that had done what needed doing and seen no particular reason to discuss it.

  "He just—" Scarab started.

  "Yes," Griff said.

  "With Valley."

  "Yes."

  "That was a plan. The dog executed a plan."

  "Scarab."

  "I'm not complaining. I'm filing it for later because I'm going to want to think about it when we're not in immediate danger."

  Don had his back to the wall, good hand pressed flat to the composite, head slightly down. The silver at his stump had faded to its baseline warmth. He looked like a man who'd just had a long conversation with something that hadn't used words, and was still working out what had been agreed.

  "It knows I'm its easiest route in," he said quietly. "Every chamber from here — it'll try to use me to tune the field."

  "Then we use you to disrupt it instead," Griff said.

  Don looked up.

  "Your thread hears it building before Valley's rig does. That's information. You tell us when it starts. We plan around it."

  Don absorbed that — the reframe. The thing that wanted him, becoming the thing that warned them.

  "All right," he said. Differently than before.

  Jake pressed briefly against his leg. Pack check. Don present. Then turned and continued up the corridor.

  Kyle had been watching the exchange with the quiet attention of someone learning a language by listening to someone who already spoke it.

  "What's the next chamber?" he asked.

  "Something harder," Valley said.

  "Than a room that tried to sync our heartbeats to its preferred tempo?"

  "It's learning what didn't work. So yes."

  Mad had been rotating his absurd hammer-axe, checking whether the jury-rigged straps had survived the crossing. They had, just. He tested the clamp. It opened and closed with a sound that suggested mild reluctance.

  "Right," he said. "Good. Fine. Onward into the next educational experience."

  "The attitude helps," Archie said. "Genuinely."

  "I'm going to need you to tell me less things that are genuine."

  "Forty-nine," Archie said, as they passed a junction.

  There was a pause.

  "Forty-nine," Mad said.

  Nobody asked what he was counting. Nobody needed to.

  Behind them the chamber went dark, its membrane cooling to baseline, the pulse migrating deeper into the structure. It logged the counter-frequency. Logged the deliberate arrhythmia. Logged the animal that barked at precisely the wrong moment and the human who followed its rhythm instead of the room's.

  It didn't feel frustration.

  It began modelling what came next.

  The crew walked on — closer now, shoulders occasionally touching, the formation slightly changed from what it had been at the top of the descent, in ways that had nothing to do with who was missing and everything to do with who was still here.

  Ahead, the corridor curved.

  The system was patient.

  It had time.