The sewer entrance beneath the abandoned Guanyin Shrine smelled of rust, stagnant water, and something far worse. Sweet rot mixed with burnt oil hung in the air like a warning. Halen descended first. His boots rang on the iron ladder that vanished into absolute darkness below. Rose followed close behind. Her crimson cheongsam whispered against the damp brick walls with every careful step. The shrine above them had long been forgotten. Its cracked stone idol stared blindly into the night. One hand remained raised in eternal blessing. The other was missing fingers broken off decades ago.
The ladder ended in ankle-deep sludge that sucked at their boots. Halen lit his qi-lantern. The soft orange glow revealed a narrow tunnel lined with ancient qi veins. Faint blue lines pulsed weakly in the stone like dying arteries. Steam vents dotted the ceiling. They hissed intermittently. Thin plumes of black-tinged vapor drifted upward and curled around the light.
Rose landed beside him without a sound. She tilted her head and listened. "The veins are still active. That's good. They will mask our qi signatures from surface patrols. The bad news is anything mutated down here will be drawn to us like moths to gaslight."
Halen wiped sweat from his brow. The vial's immunity burned in his veins. Warm. Unsteady. Like a boiler on low simmer. "How far to the lab?"
"Three kilometers. Maybe four. The tunnels fork ahead. One path leads to the old imperial qi reservoir. The other…" She glanced at him. "The other is where they tested the early batches."
Halen's stomach twisted. "Your batch."
Rose did not answer. She started walking.
The tunnel narrowed quickly. Halen had to duck under low-hanging pipes that dripped black condensate onto his shoulders. The air grew thicker. Hotter. Every few steps he felt the faint tremor of distant machinery. Perhaps the city's remaining steam works still ran on autopilot. Or perhaps something worse stirred below.
They rounded a sharp bend and froze.
A low growl echoed ahead. Mechanical. Wet. Layered with human pain.
Rose raised a hand. Three poison qi needles materialized between her fingers. Halen drew his sword. The piston hilt cycled softly with a metallic whine.
From the shadows emerged a figure. Once a man. Now something else. Brass plating covered half his face. One arm had fused into a cluster of spinning gears that whirred like a saw blade. His remaining eye glowed dull red. Black steam leaked from seams in his chest.
The thing lunged.
Halen met it head-on. Sword clashed against gear-arm. Sparks flew in bright arcs. The infected's free hand swiped low. Aimed for Halen's gut. Halen twisted aside. He drove his elbow into the creature's jaw with a piston-enhanced strike. Bone and brass cracked. The thing staggered back two steps.
Rose darted past on his left. A needle sank into the infected's neck. Green qi spread like venomous fire. The creature convulsed. Gears seized with a grinding screech. Halen finished it. Blade through the cracked boiler in its chest. Black steam erupted in a final gout. The body slumped into the sludge with a wet splash.
Halen breathed hard. "That was fast."
"Too fast." Rose knelt beside the corpse. She examined the brass plating. "This one wasn't fresh. Look at the old scarring. It's been down here weeks. The plague has had time to adapt."
Halen wiped his blade on his coat. "Adapt how?"
Rose stood. "It's learning. The virus isn't just killing. It's rewriting. Stronger hosts last longer. Smarter ones hunt in packs."
As if summoned by her words, a low clanking echoed from the tunnel ahead. Then another. And another.
Halen's lantern flickered. The blue qi veins in the walls pulsed faster. As though excited.
Rose's voice dropped. "Pack."
They backed up slowly.
Three shapes detached from the darkness. All former cultivators. Mid-Brass Gear Realm by their gear patterns. One had pistons for legs. It moved in jerky leaps. Another's arms ended in steam nozzles that hissed constantly. The third dragged a broken qi sword. Its edge glowed sickly green.
Halen's heart hammered. "We can't fight three at once down here. The tunnel's too narrow."
Rose glanced behind them. "We don't have to win. We just have to survive long enough to reach the fork."
The pack charged.
Halen roared. He overclocked both bracers. Orange qi flared along his arms in bright pulses. He met the piston-legged one head-on. Blade clashed against leaping kicks. Sparks rained down like fireflies. The thing's legs pistoned faster. Too fast. Halen blocked one strike. The second caught his shoulder. Pain exploded down his arm. He crashed into the wall. Brick cracked behind him. Blood soaked his sleeve instantly.
Rose danced between the other two. Needles flew. Green trails cut through the dark. One struck the nozzle-armed infected in the throat. It gurgled. Steam exploded from its mouth in a violent burst. The second slashed at her with the corrupted sword. Rose twisted. Cheongsam ripped at the seam. A shallow cut opened across her thigh. Blood welled. She did not flinch. Another needle sank into its eye. The creature collapsed. Twitching.
Halen pushed off the wall. The piston-legged one leaped again. He ducked low. Drove his shoulder into its midsection. Piston bracer overclocked to maximum. The impact rang like a hammer on anvil. The infected's boiler cracked with a sharp snap. Black steam jetted into Halen's face. He coughed. Vision blurred from the heat.
The thing grabbed his throat. Gears whirred in its palm. Tightening. Halen's dantian screamed. Heat surged. Too much. Too fast. The vial's immunity flickered like a dying flame.
Rose appeared behind the infected. She drove both hands into its back. Poison qi surged from her palms in twin green streams. The creature convulsed. Grip loosened. Halen broke free. Spun. Drove his sword through its core. The boiler detonated inward. The infected folded like paper. Slumped into the sludge.
For a heartbeat there was silence. Broken only by dripping water and their ragged breathing.
Halen leaned against the wall. Sword trembled in his hand. Blood dripped steadily from his shoulder. His vision swam. The world tilted.
Rose knelt beside him. She tore a strip from her already-damaged cheongsam. Pressed it to his wound. Her fingers were steady. But her eyes betrayed her. Wide. Frightened.
"You pushed too hard," she whispered. "Your dantian is overheating. The vial is failing."
Halen tried to laugh. It came out as a cough. "I noticed."
She looked up at him. For a moment the mask slipped completely. "I can't lose you down here, Halen. Not after everything tonight. Not after I finally let someone see the cracks."
Halen met her gaze. His voice was rough. Barely audible. "Then don't. Help me stand."
Rose slipped her arm under his. Together they rose.
The tunnel forked ahead. One path dimmer. Colder. The other faintly lit by red emergency lanterns that pulsed like dying hearts.
Rose pointed to the red-lit path. "That's the one. The lab. But it's guarded."
Halen straightened as much as he could. Pain lanced through his shoulder with every breath. "Then we go through them."
Rose nodded once. A tear slipped down her cheek. She wiped it away angrily.
They moved forward.
Behind them the corpses began to twitch again.
The plague was not done learning.
And neither were they.
The red-lit tunnel stretched ahead like a wound in the earth. Every step echoed louder. The qi veins in the walls glowed brighter. Redder. As though the plague itself watched them approach.
Halen's breathing grew labored. The wound in his shoulder burned hotter than the overclocked bracers ever had. Rose kept her arm around his waist. Steadying him. Her own cut on her thigh left a dark trail in the sludge.
They rounded the final bend.
The tunnel opened into a larger chamber. Old imperial qi reservoir. Massive brass pipes lined the walls. Valves the size of doors hissed open and closed in slow rhythm. In the center stood a raised platform. On it rested a shattered containment array. Broken glass cylinders lay scattered. Black residue coated everything.
And waiting on the platform were five more infected.
These were different. Taller. More armored. Brass plating covered most of their bodies. Gears spun visibly beneath translucent skin. Eyes burned bright crimson. They moved with purpose. Coordinated.
Rose's grip tightened. "These are the early test subjects. The ones that survived the initial batches. They're smarter. Stronger."
Halen drew his sword again. The piston hilt whined in protest. "How do we beat them?"
Rose pulled three more needles from her sleeve. "We don't. We break through. Aim for the boilers. Disrupt their coordination. I'll cover your left. You take center and right."
Halen nodded. "Together."
The pack charged as one.
Halen met the center one. Sword met steam-nozzle arm. The clash rang through the chamber. He ducked a follow-up strike. Drove his fist into its midsection. Piston overclocked. The impact buckled brass plating. The infected staggered. Halen pressed the advantage. Blade sliced across its chest. Boiler exposed. He thrust. Green-black steam exploded. The thing collapsed.
Rose spun between two others. Needles flew in rapid succession. One struck a gear-jointed elbow. The arm seized. The second infected swung wildly. Rose ducked. Rolled. Came up behind it. Palm strike to the back. Poison qi surged. The creature convulsed. Dropped.
The remaining two flanked Halen. One leaped high. Piston legs launching it toward his head. Halen sidestepped. The creature landed hard. Cracked the platform stone. The other fired a jet of scalding steam from its chest vent. Halen raised his arms. Qi barrier snapped up. The steam hissed against it. Heat seared his skin.
Rose appeared at his side. "Now!"
They moved in unison. Halen charged the leaping one. Sword through its exposed boiler. Rose threw her last needle into the steam-vent one's throat. Green qi detonated. Both collapsed in a heap of twisted metal and leaking fluid.
Silence fell.
Halen dropped to one knee. Sword clattered beside him. Blood pooled under his shoulder. Vision darkened at the edges.
Rose knelt in front of him. She cupped his face. Forced him to look at her. "Stay with me. We're almost there."
Halen's voice was a whisper. "I don't know if I can keep going."
Rose's eyes filled again. "You can. Because I'm not doing this without you."
She helped him stand once more.
Beyond the platform a heavy iron door waited. Red light seeped from beneath it.
The lab.
They walked toward it.
Step by painful step.
The plague waited inside.
And so did the Boiler King.