The Distillation Floor

The ink on Kester’s sounding-chart smelled of walnut gall and sour river mud. Toliman spread the sheepskin across the curved crown of the drainage vault, weighting the curled edges with his brass-toothed pipe wrench and the heavy iron housing of the captured sulfur-drill.

Beside him, Hale held the muffled tallow lamp low against the stone. The flame guttered every six paces as the draft from the breached salt-lock pulled cold, wet air across their ankles.

"Mallow said dusk," Hale said, her voice scraping like gravel turned by a spade. She pointed a scarred finger at the dense cluster of hatched lines marking the foundations of the South Depot. "The third watch changes at the bell. That gives Fletcher four hours before he drafts two dozen tenders and rolls the extraction cradle into the Grand Conduit."

"He will not wait for the third watch," Toliman said. He adjusted the wrench to hold the parchment flat against the sweating masonry. "Fletcher knows I jammed the Upper Weir. He knows the grade, he knows the filing on my keys, and he knows the only way to vent that high-tide slurry is through the South Depot's low flues. He will have the steam lines pressurized before the second bell."

Hale wiped a smear of soot from her cheek with the back of her wrist, leaving a grey trail across her puckered jawline where the vat-lime had burned away the flesh ten years before. "Then we don't go through the sluices. You said the old Water-Wardens had an intake under the bone yards."

"Not an intake. An exhaust bypass." Toliman tapped a faded brown circle scored into the sheepskin forty feet below the depot’s primary distillation floor. "When the municipality built the South Depot thirty-five years ago, they tied the sulfur retorts into the old storm flues to dump the acid vapor into the tidal flats. It was bricked over when the extraction guild expanded the vat capacity, but the outer draft casing remains. It is five feet wide, lined with cold-rolled iron plates, and runs straight under the primary battery."

Hale looked at the narrow brass cylinder of the sulfur-drill resting on the stone between them. "And it’s hot."

"It carries the counter-flow from the copper condensers," Toliman said. "The air will sit near eighty degrees. The draft will pull toward the river until the tide turns, which gives us ninety minutes to crawl two hundred paces uphill against the sulfur fumes."

"Eighty degrees and lung-rot," Hale said dryly. "A significant improvement over drowning in salt-slurry."

Toliman gathered his tools, securing the nine ward-keys on their heavy iron ring so they would not chime against his belt. He slipped the pry-awl into his leather frog beside the eighteen-inch spanner, then checked the brass feed valve on the captured drill. The tool was heavy, five pounds of solid cast bronze with three carbide sounding-tines set into its snout, designed by depot mechanics to bore through lime-crusted iron without striking a spark.

"If the draft reverses while we are inside," Toliman said, "the sulfur vapor will strip the lining from your throat in twenty breaths. Keep your mouth against your sleeve."

"I survived three months in Fletcher's lime pits, Gateward," Hale said, tucking her skinning awl into her boot shaft. "My throat was stripped before you learned which key opened the North Gate. Let's move before the tide backs up the sump."

·  ·  ·

The entrance to the old exhaust flue was hidden behind a collapsed silt baffle twenty yards downstream from the jammed Upper Weir. Toliman worked his spanner into the rusted hinge-pins of the iron grating, throwing his weight against the iron shaft until the oxidized metal cracked with the dry snap of splintering pine.

He pulled the grate outward just far enough to clear a man's shoulders. The smell that billowed from the dark interior was thick and oily, carrying the stench of boiled lard, scorched brimstone, and the sweet, cloying reek of concentrated Rot distillate.

Toliman went first, shoving the pneumatic drill ahead of him across the wet iron floor of the flue. The casing was a four-foot cylinder of riveted boiler plate, tilted upward at an angle of fifteen degrees. The metal under his palms was warm to the touch, vibrating with the distant, rhythmic thrum of high-pressure steam engines running somewhere in the earth above them.

He counted paces by the seams in the iron. Every four feet, a double row of dome-headed rivets marked an overlap in the plates. At forty paces, the air temperature rose noticeably, the draft thinning until every inhale tasted like hot vinegar. His wool tunic grew heavy with sweat, sticking to his shoulder blades as he dragged himself forward on his forearms.

Behind him, Hale crawled in steady, mechanical silence. Her breathing was harsh and shallow, a dry rattle in her chest that matched the vibration of the plates.

"Hold," Toliman whispered.

He stopped at seventy-two paces. Above them, the iron casing intersected a vertical brick riser. Through a cast-iron inspection grate set into the curve of the ceiling, a faint orange glow flickered against the soot-caked bricks.

Toliman laid his palm against the iron grate. It was searing hot, radiating enough heat to scorch wet leather. Above the grate, he heard the distinct slosh of liquid moving through heavy pipes, followed by the clanking of lead weights and the low, muffled murmur of voices.

"The solvent wash line," Hale murmured from behind his boot heel. Her voice was barely a breath against the iron. "They're priming the secondary coils. Hear that double knock? That's the diaphragm pump on the third floor."

Toliman did not look up. He focused on the seam ahead, where the iron flue narrowed into an oval maintenance bypass designed for municipal flue-scrapers. The passage dropped to barely three feet in height. To get through, he had to push the sulfur-drill ahead with one hand while dragging his spanner and key ring with the other.

The air grew thick with acrid sulfur smoke. His eyes began to water, stinging with sharp, chemical tears that blurred the dark line of the rivets. He pulled his collar over his nose, breathing through the coarse weave of wool. The grease on his skin felt slick and cold despite the rising heat, a film of industrial residue that settled in the creases of his knuckles.

At one hundred and ten paces, the flue terminated against a solid barrier: a heavy cast-iron blast door, three inches thick, seated in a granite frame that anchored the foundation of the South Depot's central retort vault.

·  ·  ·

Toliman set the sulfur-drill down with meticulous care, ensuring the steel carbide tines did not scrape the iron plate. He rolled onto his side in the cramped space, his shoulder wedged tight against the curved wall of the flue.

The blast door was secured by a double-mortise deadbolt, seated behind an external inspection boss. Above the keyhole, two copper pipes less than an inch thick ran into the masonry casing, filled with liquid mercury.

"Fire-damp triggers," Toliman said, his voice flat and low.

Hale pulled herself up beside his knee, squinting through the gloom at the polished copper lines. "If you force the bolt, the mercury column drops and trips the counterweight drops on the intake vents. It will seal this flue and flood it with live boiler steam in thirty seconds."

"I am not forcing the bolt," Toliman replied.

He unrolled his leather tool roll across his chest, selecting a pair of slender spring-steel picks and an offset tension bar. He inserted the tension bar into the bottom of the keyway, applying a light, uniform rotational pressure of barely half a pound.

The tumblers inside were ancient municipal pattern, but Fletcher's mechanics had retrofitted them with stepped serrations to catch traditional lock-picks. When Toliman lifted the first pin, the shear line did not click; instead, a faint, metallic hiss echoed through the casing as the mercury tube vibrated.

He immediately released the tension. A bead of sweat dripped from the bridge of his nose, sizzling faintly as it struck the warm flange of the door.

"The pins are grooved," Toliman said. "They are linked to the fluid balance above the cylinder."

"Can you pick it?" Hale asked.

"Not by touch alone. The springs are too heavy. If I push past the false set, the bypass valve opens."