The rust was learning to glow.
Arden noticed it first in the way the tunnel breathed.
Hours after the shrine died, Ø7 moved through a different artery of the underworks—narrower than the main trunk, ceiling lower, air thicker. Condensation clung to the concrete in greasy beads. The usual orange-brown smear of corrosion had changed; it pulsed faintly, as if lit from beneath.
Every few meters, the walls exhaled a soft, clicking hum. Not wind. Not machinery.
A hymn.
His collar tasted it before he did.
[ENVIRONMENT: SUBSTRATE AUX-CHANNEL B12.]
[CONTAMINANTS: CHEMICAL / BIOLOGICAL / SIGNAL.]
[UNAUTHORIZED TRANSMISSION: PRESENT.]
"So," he said. "Good news is the node we cooked stayed dead. Bad news…"
He swept his light along the wall.
The beam cut across veins of rust that ran like capillaries through the concrete, branching and joining. At certain junctions, the rust thickened into knots—blisters where metal had bubbled up through stone, slick and wet-looking. Those blisters glowed, faintly bioluminescent, the color of old neon reflected in puddles.
Within the glow, something flickered—tiny pulses on-off-on-off, too regular to be random.
"…bad news is the rust picked up a side gig," Arden finished.
Behind him, Kai let out a low whistle.
"That isn't chemistry," Kai said. "That's a modulation pattern."
"Translation," Seraphine said. "The fungus is singing."
Lyra stepped closer to the wall. The glow painted her cheekbones in sickly light. She didn't touch it—her fingers hovered just above the blister, like she was feeling a fever.
"It's not fungus," she said. "Not exactly. It's corrosion colonies seeded with conductive filaments. A mesh of oxidized metal and… something else. They're carrying signal through the wall."
"Please tell me 'something else' isn't people," Arden said.
Lyra tilted her head, listening.
"It's… residue," she said. "Burnt memory. Execution scraps and obedience logs. Architect-era compression. They stitched it into the rust like veins."
Architect. Arden tasted the capital letter even unspoken.
"Architect, as in the things that built the Machine?" he asked.
"Architect, as in the prototypes of what became Kairos," Kai said quietly. "Prehistoric gods. Their code is supposed to be scrubbed, deep-archived, and then ground into sand."
"Yet here we are," Arden said.
Darius shifted his weight, boots grating on damp concrete.
"Stay on task," he said. "Silex was clear. The shrine's dead, but the signal's still bleeding into adjacent sectors. Civilians are hearing things. We're here to stop the spread."
"'Civilian disturbance,' I believe was the phrase," Seraphine said. "Nice, vague way of saying 'the poor are panicking again.'"
Ahead, the tunnel kinked left, then opened into a junction. Faint light pulsed from around the bend, in time with the rust's glow.
The hymn got louder.
Not words, at first—just a binary drone, high-low, arranged in phrases. Arden's brain tagged it as nonsensical noise until a part of it, the part the collar had touched, began to recognize structure.
— 1011 001 101 —
— obey —
— rust to rust —
His skin crawled.
"Anyone else hearing that?" he asked.
"I hear it," Lyra said. Her voice had gone thin. "And something under it."
Kai's jaw clenched.
"I'm getting partial decode," he said. "The surface layer's just liturgy—Rust Saint sermon loops riding piggyback on maintenance frequencies. Underneath there's a near-subliminal band." He hesitated. "Architect signatures. Old ones."
"So the Saints plugged themselves into a god graveyard," Arden said. "Clever."
"Desperate," Lyra said. "Desperate people call anything that talks back a god."
They reached the junction.
It had once been a maintenance walkway above an overflow sump—a circular chamber with a waist-high rail and a pit of black water below. Now the rail was gone. The pit was full.
Civilians knelt in it up to their waists.
Two dozen, maybe more. Men, women, a few teenagers. Clothes soaked, skin slick with whatever floated in the water. They faced the far wall, hands clasped or held out or pressed to their chests. Eyes open, staring at the concrete.
The concrete stared back.
The wall opposite them bulged with rust colonies, dozens of blisters blooming together to form a wide, luminous panel. Within that panel, light ran in lines and curves—patterns crawling like phosphorescent mold, rearranging themselves in slow pulses.
Binary, Arden's brain supplied. Code, crawling in rust.
The kneeling people murmured in time with it.
"Rust to rust," they whispered. "Wire to wire. Signal to signal. Break the clean code. Let the dirt speak."
Their voices were small and raw. The sound bounced around the chamber, becoming bigger than it had any right to be.
Arden's collar flared, not from pain, but from proximity.
[UNAUTHORIZED LITANY DETECTED.]
[MEMETIC CONTENT: CLASS-C.]
[RECOMMENDED RESPONSE: SUPPRESS / QUARANTINE.]
"Litany," he said under his breath. "Of course it's a litany."
Seraphine took it in with one long look.
"They brought church to the sump," she said softly. "How considerate."
Darius's voice went hard.
"Priority: remove civilians from signal field," he said. "Secondary: trace structural source. Tertiary: Saints."
"Saints?" Arden asked.
He saw them then—the small cluster of figures standing knee-deep at the edge of the group, closer to the glowing wall. Rust Saints, or at least local disciples—scrap charms around their necks, halos of bent metal wired with tiny flickering diodes. One held a makeshift staff made from a broken drone strut.
They weren't armed with anything more than tools. Wrenches. Hooks. A length of chain.
No one here looked like a combatant. They looked like people who'd been kneeling for hours and forgotten what standing meant.
Seraphine's gaze fixed on the youngest kneeler.
A girl, maybe seventeen, shivering in a thin synth-fabric dress. Her lips moved with the litany. Her eyes didn't blink.
Seraphine exhaled.
"I've got the crowd," she said.
Darius shifted his stance.
"You step into the water, you may get infected," he said. "Metaphorically or otherwise."
"Then stay dry," she said. "Someone has to talk them out before your 'suppress and quarantine' turns into bullets and bleach."
Arden's collar pinged.
[COMMAND DISPUTE FLAGGED.]
"Relax," he muttered at it. "He hasn't actually ordered a massacre yet."
Silex's voice slid into his ear.
"Don't tempt fate, Reik," Silex said. "Update."
Arden flicked his chin to transmit.
"Found your disturbance," he said. "Biolum rust wall broadcasting Rust Saint liturgy. Two dozen civilians waist-deep in sewer, repeating it like a hymn. Local Saints supervising. No weapons beyond hand tools."
"Any signs of escalation?" Silex asked.
"Depends what you call escalation," Arden said. "The rust's carrying Architect residue. Lyra's twitching. My collar's giving memetic warnings. I'm calling it a bad church."
"Containment priority," Silex said. "Memetic leakage into civilian population is unacceptable. You will remove them from the field. Non-compliance from cult adherents can be met with lethal force."
"Copy," Darius said.
"Reik," Silex added. "If the litany begins to affect your team, I will trigger leash overrides. Do not let it get that far."
"Nice pep talk," Arden said.
He cut the channel.
Seraphine shrugged off her rifle, clipped it to a rail post, and stepped toward the flooded pit.
"Vega," Darius warned.
She stopped at the edge, looked back at him.
"Trust me," she said. "This is one of those rare moments where shooting first makes everything worse."
There was a weight under the lightness of her tone. Arden saw Darius weigh it—the civilians, the litany, the handler's orders, Seraphine's particular talents.
He nodded once.
"Forty-five seconds," he said. "Then we move in."
"Make it ninety," she said. "Have some faith."
"Forty-five," he repeated.
Her mouth twitched. "You're adorable when you compromise."
She stepped down into the water.
It swallowed her boots with a thick, sucking sound. Whatever floated in it clung to her pants in strands. She grimaced once, then smoothed it away.
"Hey," Arden called after her. "If you grow extra eyes, I'm not kissing all of them."
She gave him a two-fingered salute without looking back.
Then she walked into the congregation.
⸻
Up close, the litany pressed against Seraphine like humidity.
Arden watched from the edge, rifle ready, safety off.
Her shoulders tightened as she passed behind the first row of kneelers. The girl in the cheap dress didn't react. The man beside her—middle-aged, bald spot shining in the rustglow—kept murmuring.
"Rust to rust. Wire to wire…"
Seraphine crouched between them, laying one light hand on each shoulder.
"Hey," she said, voice low, almost conversational. "You're going to shred your vocal cords if you keep that up."
No response.
Her mouth twitched.
"You know what they forgot to tell you?" she said. "Gods don't live in walls. They live in people. And the people who run this dome need you upright, breathing, and capable of paying your debts, not drowning in a sewer."
A slight flicker in the girl's eyes.
Arden sucked in a breath.
Seraphine pressed her thumb gently into the muscle of the man's neck, just below the ear. A pressure point, not enough to hurt, just enough to remind his body he existed.
"Look at me," she said.
The man blinked.
His lips kept moving, but the word shape lost cohesion.
Seraphine's smile was small and warm—no edge, no flirtatious curl. Just kindness, practiced like a weapon.
"There you are," she said. "Do you remember where you are? You're not in some holy river. This is sewer overflow channel B-twelve. It's full of things that will give you infections with names."
He frowned.
"The saint—" he started.
"Is very flattered you came," she said quickly. "He told me himself. I'm one of his messengers." She tapped the side of her own collar, as if it were ornament rather than shackle. "But he also told me there's going to be a flush in about ten minutes. High-pressure backwash. If you're still here when that hits, you're going to be carried into a processing grinder. He doesn't want that."
The man's gaze flicked toward the rust wall, then back to her.
"He… doesn't?" he said.
"No," Seraphine said. "He's quite specific about it, actually. He loves your little prayers. He wants you to keep saying them—just not here. Not in the water. He'd really prefer you do it somewhere warm, with dry socks."
The girl's lips faltered.
"Dry socks," she repeated faintly.
"Yes," Seraphine said. "Have you ever tried devotion with dry socks? Revolutionary experience."
A tiny laugh escaped the girl. It sounded like it hurt.
Seraphine seized it like a lifeline.
"There it is," she said. "That sound? That means you're still you. Congratulations. Now, I need you to stand up. Slowly, because if you fall you're going to splash some truly unspeakable things onto me, and I will cry, and no one wants that memory."
She eased them both to their feet, using hands and voice and gaze like tools. The litany faltered around them.
A few of the other kneelers blinked, destabilized by the disruption in rhythm.
One of the Saints waded toward her, staff held across his chest.
"Leave them," he said. His voice had the rough edge of someone who'd spent too long shouting over machinery. "They're under protection. The Machine can't see them here."
Seraphine turned her head toward him.
Rustglow painted her hair copper, her eyes dark.
"You're right," she said. "The Machine can't see them. But you know what can? The bacteria in this water. The rats. The parasites. They don't care that you call this a holy bath. They're going to eat your saints from the toes up."
He hesitated, staff dipping.
"Our Prophet said—" he began.
"Your Prophet," she said gently, "is in custody, arguing theology with people who have much bigger guns than you. He's not here. I am. And I am telling you the only way you get to keep praying is if you get out of the pit now, before my commanding officer decides you're contamination instead of congregation."
She let a sliver of steel into her tone on the last word.
The Saint flinched.
His eyes flicked past her to the dark figures on the rim—Darius, still as a statue, rifle leveled; Arden, lean and dangerous; Lyra, pale and listening; Kai, fingers hovering near his console.
"Dogs," the Saint whispered. "You brought Dogs into a holy place."
Seraphine's smile sharpened, just a little.
"You dragged your congregation into a sewer," she said. "Call it even."
Arden saw the moment the Saint weighed his choices. Piety against survival. Faith against fear.
Something in his shoulders crumpled.
He lowered the staff.
"If we leave," he said, "will you kill our saint?"
Seraphine's gaze flicked to the rust wall.
The bioluminescent colonies pulsed with binary still, though the pattern had shifted. Not purely Rust Saint liturgy now. Something older bled through. Architect residue whispering in the gaps.
She didn't look away.
"No," she said softly. "We're going to move it."
The Saint frowned.
"Move it?" he repeated.
"Evacuate the signal into another container," she said. "Somewhere it can't bite civilians. Think of it as… a pilgrimage. Your saint goes to a higher temple for a while."
That was a lie.
Mostly.
Kai was already working on jury-rigging a portable capture unit, a box of scavenged hardware and Bureau-grade dampeners. They'd try to siphon as much of the signal as possible into it. What survived would go to Silex's labs. What didn't would die in the rust.
But she said it like a promise, not a sentence.
The Saint looked at her for a long time.
Then he nodded, once.
"Brothers, sisters," he called. "Up. The saint is moving on. We're escorting him to a safer crypt."
The words passed through the congregation with the authority of habit.
People began to stir.
Not all at once; some had to be coaxed, dragged, physically supported. Seraphine moved among them like she'd been born to it—hands steady, voice low, lying with the ease of someone who knew exactly how much truth to include to make the poison palatable.
"You're chosen," she told an old woman whose lips were cracked from repeating the litany. "He heard you. That's why you're leaving first."
"You're brave," she told a boy with a rust-laced halo around his brow, the metal having left irritant burns on his skin. "Only the real faithful survive the exit trial."
"You did enough," she told a man clutching a corroded charm. "More than enough. Your saint doesn't want your corpse. He wants your story."
Lies, stacked on half-truths, cemented with the one thing that made all of it bearable: she meant the kindness. She wanted them to live.
It leaked into her voice.
Arden felt his own chest loosen.
The litany in the chamber changed.
"Rust to rust… wire to wire…" faltered, became "Wait… watch your step… hold my hand…"
The binary hum didn't vanish, but it lost its teeth.
On the rim, his collar cooled by a degree.
[MEMETIC UPTAKE: REDUCING.]
Silex pinged him.
"Status," the handler said.
"Seraphine's doing her messiah cosplay," Arden said. "It's working. Civilians are disengaging from the litany. You might not need to blank them all and start over."
"I wasn't planning to blank them," Silex said mildly. "That's expensive. Amnesia protocols cost more than bullets."
"You always know just what to say," Arden said.
He cut the channel again before the handler could reply.
Lyra moved to the edge of the pit, staring at the wall.
Now that the crowd was thinning, the glow seemed brighter, thrown into sharper relief. The rust blisters were no longer just random colonies; they outlined something like a rough mandala, a pattern spiraling inward.
At the center of the spiral, a darker patch of wall sat like a pupil.
Lyra's fingers twitched.
"What is it saying now?" Arden asked her.
She didn't answer at first.
Her head canted, listening to something he couldn't hear.
Then:
"It's not a sermon anymore," she said. "It's… diagnostics. Heartbeat checks. It's looking for something it lost when we killed the shrine. A missing node."
Arden's stomach tightened.
"Crohn's saint?" he asked.
"The node in the junction," she said. "It was a heart. This is an artery. The system is aware of damage and is trying to reroute flow."
"System," Kai said, coming up beside them, knees splattered with sump!muck. "As in Rust Saint system, or as in The System?"
Lyra's mouth tightened.
"Yes," she said.
Kai raked a hand through his hair, leaving streaks.
"Love that clarity," he said.
He knelt by the glowing wall, setting down a compact device that looked like a square metal canister wrapped in mesh and tattoos of cabling.
"Portable signal cask," he said. "Very illegal. Very experimental. Very likely to explode. I'm going to try to convince the rust to pour its song into this instead of the collar network."
"Can you do that without touching it?" Arden asked.
"Physically? Yes. Psychologically? Probably not." Kai glanced at Lyra. "I'll need a translator. You up for an encore after your little possession stunt back at the shrine?"
Lyra swallowed.
"It's not possession," she said. "It's… hosting. Briefly."
"That's so much better," he said. "Come on."
She stepped down beside him, boots sinking in muck.
The last of the civilians were being hauled out now. Darius supervised the line, his presence a calm gravity that pulled people toward him. Seraphine circulated at the back, checking for stragglers.
One older woman refused to let go of the rust wall until Seraphine opened her own collar casing just enough to show the metal beneath.
"See?" she told the woman. "He's still talking. You can hear him through us now. You don't have to stay."
The woman wept. Then she let go.
Arden had to look away for a second.
Kai powered up the cask. The mesh hummed, faintly, like a tuning fork.
"Okay, Ghost-Eyes," he said. "Tell the wall there's a better home. Less… damp."
Lyra pressed her palm near the central spiral, not quite touching the rust.
Her pupils blew wide again.
"The Architect residue is… curious," she whispered. "It remembers being bigger. It remembers halls of light, not sewer walls. It's offended. But it's tired."
"Sell it on retirement," Kai muttered. "Nice quiet canister upstate. Fresh air, no handler."
Lyra's throat worked.
"Come down," she murmured. Arden couldn't tell if she was talking to the rust or to herself. "Come down from the walls. We'll take you to the heartline. You don't have to rot alone."
A beat.
The glowing blisters pulsed brighter.
Then, slowly, their light began to dim—and the cask began to glow.
Signal shifted, leaving rust, flowing along embedded filaments and invisible channels into the device. The binary hum in the chamber dropped in pitch, then volume.
Arden's collar pinged data.
[UNAUTHORIZED TRANSMISSION: REDIRECTED.]
[MEMETIC HAZARD: NEUTRALIZED (LOCAL).]
He hadn't realized how tight his shoulders were until they loosened.
The portable cask's glow steadied.
Kai exhaled.
"Got you," he said softly. "You beautiful, horrible thing."
Lyra staggered.
Arden stepped in without thinking, catching her by the elbow.
She was cold and shaking.
"You good?" he asked.
She blinked up at him.
For a moment, her eyes were full of things that weren't there—corridors of light, screaming glass, statues of data.
Then they cleared.
"It knows the word 'heartline,'" she said. "I thought it was just cult nonsense, but… no. It's a path. An internal designation. Something the Architects built. The Rust Saints just… overheard it."
"File that under Problems For Later," Arden said. "Right after 'what happens when Silex plugs that box into his toys.'"
Kai sealed the cask, locking clamps with brisk motions.
On the opposite side of the chamber, Darius finished counting heads.
"All civilians accounted for," he called. "Minimal injuries. No visible lesions."
"Excellent," Silex said dryly in Arden's ear. "You've saved some of my tax base. Bring the cask and any cooperative Saints to the extraction point. Leave the rest; cleanup units will sanitize the area."
Arden looked at the drained rust wall.
Without the glow, it just looked like what it was: disease. Flaking brown, blistered concrete, streaked with the outline of where the litany had been.
He thought of Crohn, on their knees in the shrine. Of the saint they'd built and lost. Of their bitter little truth: Rust gets in through the smallest cracks.
"Sanitize," Arden repeated. "With what? Acid? Fire? Another leash purge?"
"Standard industrial solvents," Silex said. "Relax. I'm not going to burn the whole underworks just to erase some graffiti."
"Yet," Arden said.
Darius herded the civilians toward a side tunnel, where CAD medtechs in sealed suits waited behind a hastily erected decon frame. The Saints clustered together, murmuring misaligned prayers.
Crohn wasn't among them. Crohn belonged to another team now, another room, another set of questions Arden didn't get to ask.
Seraphine waded back through the now-empty sump, boots squelching, pants soaked to the thigh.
"You owe me new clothes," she told Arden.
"Bill the Bureau," he said.
"I did," she said. "They sent a pamphlet on mindful consumption and a voucher for a discount halo."
Arden snorted.
She reached the edge, took his offered hand. For a moment, their fingers slipped in muck. Then they locked.
He pulled her up.
Their faces ended up close. Sewer stench, rust tang, her breath warm despite it all.
"Nice lies," he said quietly.
"They weren't all lies," she said. "I meant the part about dry socks."
"Yeah?" he said. "What about 'he heard you' and 'you're chosen'?"
She hesitated.
"I meant those too," she said. "Just not the way they thought."
There was something in her eyes—a tired anger, an unwilling tenderness.
He nodded, once.
"Fair," he said.
Lyra watched them from the side, expression unreadable.
Kai hefted the cask, muscles complaining.
"This thing is heavier than it looks," he said. "Whatever's inside it does not want to be portable."
"Welcome to being alive," Arden said. "Nobody asked us if we wanted to be portable either."
As they started back down the tunnel, rustglow fading behind them, the hymn tried one last time.
"Rust to rust," a whisper rose from the walls. "Wire to wire—"
Lyra lifted her hand.
"Enough," she said.
The whisper cut.
The tunnel fell silent, except for their footsteps and the distant drip of water.
Arden's collar hummed, low, almost content.
[OBEDIENCE LATTICE: STABLE (LOCAL).]
It wouldn't last. Nothing did down here.
But for now, the litany of decay had been smothered.
Or bottled.
Same difference, in this city.
Halfway back to the ladder, Kai stumbled.
The cask slipped in his grip. Arden caught it before it hit the floor. For a second his palms were pressed to its metal skin.
Heat pulsed under his hands.
Not physical. Not entirely.
A throb of something like a heartbeat. A fragment of signal.
In his head, a whisper:
— variable zero —
He snapped his hands back.
"Problem?" Darius asked.
"Just thinking about early retirement," Arden said.
He passed the cask back to Kai.
Lyra's eyes were on him now.
"You heard it, didn't you," she said.
"What?" he asked.
"Nothing," she said.
She was lying. Badly.
He let it go.
One crisis at a time.
Behind them, the rust on the walls dimmed, its glow receding like tidewater.
Ahead, the ladder up gleamed with condensation. Above that, CAD staging lights. Up there, paperwork, labs, interrogations, all the clean ways to reframe what had just happened into something palatable.
Down here, in the dark, the city had sung to its own rot.
They'd changed the tune.
For now.