The ducts always sounded like something breathing.
They crawled single file, Ren in front because he knew which cameras he'd already lied to, Sumi behind because she insisted she could feel the turns better when she could mutter the route under her breath.
"Left— left— no, wait—" her fingers hesitated on a seam, then shifted, "right, up— then left again. If we hit a fan, we overshot."
Condensation kissed their skin, colder in some stretches than others. In one bend the metal held the night's chill and leeched heat from his palms; in the next it sweated warm against his forearms. Their shoulders banged the duct at every awkward angle, the sound coming back at them louder than it should, doubled in the tight space. Sometimes they had enough room to keep their limbs human; sometimes they had to shrink down mid-crawl, bones tightening inward with a dry click that threw off his rhythm, palms flattening to paw-pads so they could wriggle through tighter throats.
Ren's nose filled with the tower's layered scents. Bleach, human sweat, ozone. Under it, copper—fresh in one stretch, old in another—where someone had bled into the dust. Old fear sat in the metal like something baked in.
They passed vents.
Air pushed through the slats in thin streams, carrying pieces of other rooms with it.
A chemical-sweet reek first—he glanced down despite himself. Kids, not much younger, strapped in, machines ticking in a forced rhythm that didn't quite match their chests. One of them hitched a breath off-beat. Ren's shoulders locked; he moved on before his hands forgot what they were doing.
Heat next, sharper. He looked and regretted it. A body on a table, opened, foxfire leaking out in threads that made a faint, high sound he could feel in his teeth. His grip slipped on the metal. He dragged himself past.
Salt and grease after that. Laughter from a box, too loud, too regular. Three staff bent over bowls, not looking up. Sumi lingered a fraction too long behind him; he heard her breath hitch, then flatten.
"How long—" she started, then stopped as he took a turn too fast and banged his shoulder.
"T-junction," she corrected under her breath. "Wait."
They paused there, bodies pressed to metal, both listening to nothing in particular.
"How long have you been stuck here?" she asked again, quieter.
"Long enough," he said.
"Before—"
"Road." He pulled himself up the right-hand shaft. "Hunters—" his elbow slipped; he caught himself, hissed, kept moving, "—caravan. One of them sold me instead of a crate of salvage."
"Didn't—" she began.
"Didn't catch me as fast as they thought." His breath came shorter for a few pulls.
Sumi swore softly behind him.
She saved her own answer for the next bend, voice breaking once in the middle like she'd bitten it off and started again.
"City grabbed me for— for talking back to a scanner. It didn't like the way I sounded. Numbers came out wrong." A pause. "Somebody higher up— wanted to see why. I— didn't—" she exhaled hard, "—cooperate."
"So they subcontracted it," Ren said.
"Contractors love a—" she shifted, metal squealed under her weight, "—a puzzle."
They hit the section with the duct cameras and both stopped without speaking.
The air changed first. Warmer. A low, steady hum under the metal, like something thinking. Ren could feel it through his forearms.
A faint red glow pulsed ahead.
"Wait," he whispered.
Neither moved.
The duct narrowed there, squeezing them into it. No branch, no gap. Go forward or go back.
Sumi's fingers tapped once against the metal behind his ankle, then stilled.
"You feel that?" she breathed.
"Yeah."
The hum ticked against his teeth.
Another pulse of red.
He swallowed, tasted iron.
"No clean way around," he said.
"Then—" she stopped.
Another pulse. The hum shifted, just enough to feel like attention.
Ren let the foxfire rise anyway.
It came wrong at first. Too fast. Heat climbed his throat; his vision smeared sideways, the red light dragging a tail behind it. He blinked and it didn't fix. The duct seemed to tilt.
"—wait," Sumi hissed.
Too late.
He pushed.
The metal in front of him… dulled. Not vanished—just wrong. Flat. Empty in a way that made his eyes ache trying to hold it there. The hum pushed back, a faint shiver through the duct like something tapping from the other side.
His nose went wet.
By the second camera, the pressure behind his eyes sharpened into a spike. The red glow doubled, then snapped back. Something in the duct flickered—just a blink—and for that blink the space filled itself back in, real and watching.
"Ren," Sumi said, sharper now.
"I know."
He dragged the false-stillness back over it, sloppier this time. The edges crawled.
By the third, the hum changed. Louder. A stutter in it, like a question.
The sound behind him didn't match his movement anymore.
His elbow scraped forward—behind him it came a beat late.
"Stop," Sumi whispered.
He froze.
The mismatch hung there, wrong.
"You're ahead of it," she said, breath quick. "Your sound's— lagging—"
Another flicker. The red light sharpened.
"Fix it," he said through his teeth.
A sharp snap behind him.
The air shifted.
The scrape, their breathing, the small ticks of metal—something caught them, bent them, pushed them back into place. For a second it all doubled—two sets of breaths, two scrapes—then one swallowed the other.
Ren pushed again.
The hum steadied, not convinced but not alarmed.
By the fourth camera his vision tunneled. Water ran from his nose onto the metal; he didn't wipe it. The empty duct in front of him shivered, threatened to fill.
"Almost," Sumi murmured, voice tight now, less sure. "Keep— keep it—"
He did.
They slid past the last red eye.
For a moment nothing happened.
Then the hum dropped off behind them like a held breath released.
Ren moved one more length of duct and stopped because his arms stopped listening. He sagged against the metal, breath hitching out of rhythm, fingers twitching where they gripped.
Sumi bumped into him from behind, harder than she meant to.
"Move—" she started, then heard his breathing and stopped. "—okay. Wait."
They lay there, both of them pulling air that felt too thin.
"New rule," she said after a second, voice rough. "If either of us says 'this is easy,' the other gets to hit them."
"Deal," Ren said. The word came out crooked. He dragged the back of his hand under his nose; it came away dark.
They crawled on.
Eventually they hit the hatch labeled ROOF MAINT ONLY.
The metal around it felt different—thicker, colder. The seam pressed into his shoulder when he leaned into it.
He shoved.
Nothing. The impact ran back through his arm and sat in his joint.
Sumi shifted beside him, digging in her pocket. Metal clicked faintly as she sorted through it.
"On three," she said. "You push. I—" she wedged the strip into the seam, breath hissing between her teeth as it slipped once, "—I make it give."
"Who taught you—"
"Same people who locked me—" she cut herself off. "Three."
They shoved.
Foxfire came up again, slower this time, heavier. It sat wrong in his shoulder, like pressure where there shouldn't be any. The hinge resisted, then gave a fraction.
Rust screamed.
The sound was too loud in the tight space. Ren flinched; the pressure slipped. The hatch slammed back a hair.
"Again," Sumi snapped.
They shoved.
Something popped.
The hatch tore free.
They spilled through into the maintenance stairwell, concrete scraping skin where metal had before. The air hit different—thicker, damp, carrying the smell of wet dust and old water. Sound changed too; their breaths echoed back at them, stretched.
Ren pushed himself upright and almost didn't make it; his knees lagged a beat behind the motion. He caught the wall, jaw tight, waited for the floor to settle.
Rain hammered somewhere above, the noise heavy and directionless.
"Up," he said.
"Up," Sumi agreed, already moving, one hand trailing the wall like she didn't quite trust it.
They climbed.