The siren that cut through the smog of Cinder wasn't the shift whistle. It wasn't the fire alarm. It was a sound that made the marrow of every slave on the island turn to ice.
It was a low, oscillating drone, like the hum of a dying wasp.
The Audit.
Kael froze, his charcoal stick hovering over a blueprint of the secondary cooling array. In the Iron Sultanate, an Audit didn't mean counting inventory. It meant counting sins. It meant the Grand Artificer's logic-engines had detected a statistical anomaly in the output—a drop in efficiency, a missing crate of rivets, or a spike in unauthorized chatter—and sent a team to correct the variance.
Usually, they corrected it with a bullet.
The heavy door of the Design Tower slammed open. Kael didn't flinch. He carefully set down his charcoal, wiping his soot-stained hand on his rag of a tunic.
"Unit 734," a guard barked. This one was wearing the crimson shoulder-pauldron of the Inquisition. "The Baron requires your presence in the Processing Center. Immediately."
Kael slid off his stool. His left leg, stiff from an old break that had never set right, protested. "Is there a malfunction, officer?"
"Move, cripple."
Kael limped into the corridor. The air tasted different today. Sharper. The smell of ozone was stronger than the usual sulfur.
As they descended the spiral stairs of the tower, Kael ran the variables through his mind. The Flux-Valve was installed four hours ago. Adam was precise. The pressure shouldn't be showing on the main gauges yet. Did someone talk? Did they find the tunnel?
They marched him out of the Tower and across the suspended catwalks that overlooked the main refinery floor. Below, thousands of workers had stopped. They stood by their machines, heads bowed, terrified to move.
In the center of the factory floor, a clearing had been made.
Baron Vance stood there, looking immaculate in his white coat, flanked by two Iron-Spiders—massive, six-legged automatons powered by steam and clockwork, their brass mandibles clicking softly.
But Kael's eyes went to the chair in the center of the clearing.
It was the "Truth-Seat," a rusted iron chair bolted to the floor, fitted with pneumatic restraints.
And strapped into it was Miller.
Kael's heart hammered against his ribs. Miller was an old man, a former clockmaker from the capital who had been enslaved for debt. He was also the one who had distracted the guards while Kael stole the valve schematics three months ago.
Miller looked bad. His face was swollen, one eye shut. He was weeping silently.
Standing over him was a man Kael had only heard rumors of. He was tall, wearing a leather apron over a bare torso that was modified with subdermal tubing. His skin was pale, almost translucent, and his eyes were replaced with red optical lenses.
The Auditor.
"Ah, the genius of the tower," Vance said, spotting Kael. He beckoned him down the stairs. "Come, 734. We have a discrepancy."
Kael descended the final steps, his face a mask of indifference. He forced the Healer deep down into the dark recesses of his mind. The Healer would weep for Miller. The Engineer needed to calculate the vectors of survival.
"My Lord," Kael said, bowing his head.
"We found a discrepancy in the inventory," Vance said, gesturing to a table covered in scrap metal. "A brass valve is missing from the recycling sorter. A Class-A pressure rating. The Auditor here believes it was stolen."
The Auditor turned to look at Kael. His voice was synthesized, a buzz of static and gravel. "The old unit claims he knows nothing. But his heart rate suggests... deception."
"Miller is a clockmaker, My Lord," Kael said calmly. "He works in assembly, not recycling. He wouldn't know a pressure valve from a piston."
"He was seen near the scrap heaps," Vance countered, his mechanical monocle spinning. "And now, he refuses to tell us who he was meeting."
The Auditor stepped closer to Miller. He held a device in his hand—a Hydro-Lash. It was a terrifying piece of engineering: a handheld nozzle connected to a high-pressure portable boiler on his back. It fired a stream of boiling water thin enough to slice through bone, but the Auditor had it set to 'spray.' It stripped skin without killing the host.
"Pain is a variable," the Auditor buzzed. "Sufficient application yields truth. Always."
He raised the nozzle.
"Wait," Kael said.
The word hung in the air. Vance raised an eyebrow. The Iron-Spiders shifted, their steam-vents hissing.
"I am the Senior Engineer of this facility," Kael said, keeping his voice steady. "If that unit is damaged beyond repair, production in Sector 7 drops by 0.5%. Miller aligns the gear-teeth for the conveyor. No one else has the dexterity."
Vance waved a hand dismissively. "Replaceable. Everyone is replaceable."
"Not before the Emperor's inspection," Kael said. "Training a new alignment specialist takes three weeks. You have five days."
Vance paused. The logic landed. The Baron cared nothing for life, but he cared deeply for his schedule.
"The Auditor does not need to kill him," Vance said. "Just... motivate him."
The Auditor adjusted a dial on the Hydro-Lash. "I will remove a finger. It will not impact his dexterity. The thumb is essential. The pinky is not."
Kael looked at the device in the Auditor's hand. He analyzed it in a split second.
It was a standard-issue suppression tool, Model IV. It relied on a flexible high-pressure hose connecting the tank to the nozzle. The hose was reinforced rubber, rated for 3000 PSI.
But Kael noticed something. The Auditor was standing directly over a grate that vented heat from the sub-floor furnaces. The rubber hose was trailing on the hot metal.
Heat softens rubber.
Expansion coefficient.
Tensile strength failure.
If the Auditor fired that lash at full pressure while the hose was superheated, the rubber wouldn't hold. It would burst. But a burst hose would just scald the Auditor's leg. It wouldn't stop him. It wouldn't save Miller.
Kael needed a catastrophic failure. He needed the tank to blow.
"The pressure regulation on that Model IV is faulty," Kael said suddenly.
The Auditor froze. He turned his red lenses toward Kael. "You question my equipment, slave?"
"I question the maintenance," Kael lied smoothly. "The humidity in Cinder causes corrosion in the intake valves of those tanks. If you fire it at that setting, the back-pressure might cause a jam. You won't get a clean cut. You'll just mangle the hand."
Vance looked at the Auditor. "Is this true?"
"My gear is pristine," the Auditor snarled. To prove it, he cranked the pressure dial to the maximum red line. "I will demonstrate on his left hand. A clean severance."
Kael stepped closer, feigning subservience. "My Lord, permit me to adjust the flow? If you want a clean cut, the aperture needs to be narrowed. Otherwise, the spray radius is too wide. You'll damage the nerve endings in the palm."
Vance nodded. "Do it. Quickly."
Kael stepped up to the Auditor. The man smelled of sterile alcohol and burnt meat. Kael reached out with his one hand to the nozzle.
"Don't touch me, filth," the Auditor hissed, but he held the weapon out.
Kael's fingers moved with the dexterity of a surgeon. He twisted the nozzle aperture.
"Tightening the focus," Kael murmured.
In reality, he wasn't tightening the focus. He was threading a tiny metal shaving—a piece of scrap he had palmed from his pocket earlier—into the release trigger.
Then, his hand brushed the intake coupling near the tank on the Auditor's back. With a flick of his thumb, he disengaged the safety release valve. It was a subtle click, masked by the roar of the factory.
"Done," Kael said, stepping back quickly. "But I would advise standing back, My Lord Baron. The spray is... potent."
Vance took a step back.
The Auditor sneered. He turned back to Miller, who was shaking, his eyes wide with terror.
"For the glory of the Machine," the Auditor intoned.
He squeezed the trigger.
The metal shaving Kael had inserted prevented the trigger from depressing fully. The valve opened only halfway.
The water, pressurized to 4000 PSI, hit the obstruction.
Physics took over.
The water couldn't exit the nozzle fast enough. The pressure wave rebounded instantly, traveling back down the hose at the speed of sound. Usually, the safety release valve on the tank would pop open to vent the excess pressure.
But Kael had closed it.
The pressure slammed into the tank on the Auditor's back. The tank, already weakened by the ambient heat of the foundry, found its weakest point: the coupling right behind the Auditor's neck.
CRACK.
It sounded like a cannon shot.
The coupling failed. The tank didn't just leak; it detonated. A jet of superheated steam and boiling water exploded directly into the base of the Auditor's skull.
The Auditor didn't scream. He simply arched backward, his spine snapping audibly from the force of the blast. The tank ripped itself free from the straps, launching into the air like a misguided rocket, spinning wildly before crashing into a stack of crates.
The Auditor collapsed, a ruin of steam and cooked flesh.
Silence fell over the factory floor.
Miller sat in the chair, unharmed, staring at the smoking corpse of his tormentor.
Vance shielded his face with his sleeve. He coughed, waving away the steam. He looked at the body, then at Kael.
Kael stood perfectly still, his face impassive.
"I warned him," Kael said softly. "The intake valves. Corrosion causes back-pressure spikes."
Vance stared at Kael for a long, uncomfortable moment. The monocle whirred, zooming in on Kael's face, searching for a smirk, a bead of sweat, a flicker of satisfaction.
Kael gave him nothing. Just the blank stare of a machine.
"Incompetence," Vance spat, kicking the Auditor's motionless boot. "They send me butchers when I need scientists."
Vance looked at Miller. "Get him back to the line. If he misses his quota by one gear, feed him to the spiders."
"Yes, My Lord," Kael said.
He moved to unbuckle Miller. The old man was trembling so hard his teeth rattled. Kael leaned in close, pretending to check the restraints.
"Breathe, Miller," Kael whispered, his voice barely audible. "The valve?"
"Safe," Miller wheezed, tears cutting tracks through the soot on his face. "I didn't talk. I didn't..."
"I know," Kael said. He helped the old man stand. "Go. Work. Survive. Four more days."
As Miller hobbled away, Kael looked down at the Auditor. The water was pooling around the corpse, mixing with the grease of the factory floor.
Kael felt a sickness in his stomach. The Healer in him was horrified by the cruelty of the method. He had engineered a man's death as easily as he engineered a bridge.
But then he looked at the collar around his neck. He looked at the thousands of slaves watching from the shadows.
Physics, he reminded himself. Action and reaction.
The Auditor applied force. Kael simply redirected it.
"Unit 734," Vance called out, already walking away. "Clean this mess up. And recalibrate the remaining Hydro-Lashes. I won't have my equipment failing during the inspection."
"At once, My Lord," Kael replied.
He knelt beside the body to retrieve the tank fragments. As he did, he saw something glinting in the pool of water. It was the metal shaving he had used to jam the trigger.
He picked it up and slipped it back into his pocket.
The system worked.