The Heat Through the Leather

When a chimney stops drafting in Cadernera, it usually means soot crust or a dead bird; it rarely means three yards of chitin webbed across the brickwork with boiling pitch. The heat radiated through my leather boots before I even dropped my scrapers down the stack.

"Pump it up to three bars, Lázaro," I said, crouching by the rim of the masonry. "Not four. The copper seals on this rig are older than you are, and I have no desire to pick brass shrapnel out of my shins."

Behind me on the steep slate pitch, Lázaro worked the twin pump handles. The boy was fourteen, thin as an iron poker, his face smeared with grease and black dust until only the whites of his eyes showed clearly. He leaned his weight into the strokes, his chest wheezing on every down-beat. A dry, rattling cough broke from his ribs, rattling against his teeth. He spat a plug of grayish phlegm onto the slates and wiped his chin with his soot-cloth.

"Piston's sticking, Master Mateiro," he said, breathing hard. "The valve leather is drying out from the exhaust."

"Spit on the gasket and keep pumping," I told him. "We don't get paid six copper groats if Trilla's tenants suffocate before dinner."

Above us hung the true ceiling of Cadernera: the great canopy. Thousands of tons of bolted wrought iron arched from district wall to district wall, trapping every breath of coal smoke, grease vapor, and sulfur exhaust the factories below could belch. No sun had touched the city since my grandfather's youth. The only light came from the municipal gas fixtures mounted on exterior brackets and the dull, yellow flare of street lanterns sixty feet below our rooftop perch. Out here in the lower wards, the air tasted of scorched tin and vinegar. You breathed it through linen or you died coughing blood before your thirtieth winter.

I adjusted my heavy goggles. The left lens was clear glass, but the right covered an eye half-ruined by an acid backfire eight years back. Through the milk-white haze of that scarred pupil, the city looked like a blurred smear of charcoal and sputtering yellow flame. But my ears and hands were sharp enough to make up for what the chemicals took.

Casa Trilla was a four-story boardinghouse packed with fifty weavers, grease-pressers, and dock laborers. Trilla himself, a squat man who bought third-grade sulfur briquettes to save copper and then complained that his parlor smelled like a copper smelter, had pounded on my cellar door at midday. The top two floors were filling with oily black smoke that burned the eyes and made the children vomit. Trilla had sworn the chimney simply needed a routine reaming with the iron chain.

Trilla was a fool.

I pulled off one thick leather work glove and spat directly onto the outer brick of the stack. The spit sizzled instantly, boiling away in a gray puff of steam.

I took the short scraper from my belt and jammed the steel blade into the flue's lip, prying away a ring of baked soot. The iron scraped through crust and caught on something gummy and fibrous that wouldn't flake. To test the draft, I struck a sulfur match against my thumbnail and held the flame over the dark shaft.

A healthy chimney would swallow the flame, pulling it downward and upward with the draw. Here, the match flame flattened, sputtered green from trace coal-gas, and suffocated in stagnant heat. This flue had no draw at all. The heat hovered in a dead, trembling column, carrying a stench that wasn't creosote or unburned fuel.

It smelled like roasted bone and scorched axle grease.

"Hold the line steady," I said, reaching for my chain harness.

Lázaro took the anchor rope, bracing his boots against the roof ridge. His small hands were calloused and black-creased, steady despite the tremors in his lungs. He knew his trade. When a sweep lost his footing on the slick slate of Cadernera, nobody came looking until the street sweepers scraped the mess off the cobblestones the next morning.

I took the lead weight—a ten-pound iron plum wrapped in spiked steel fins—and swung it over the dark mouth of the chimney.

"Dropping," I said.

I let out two yards of heavy hemp rope. The weight slipped into the darkness. There was no scrape of metal against dry brick. No comforting shower of loose soot cascading down toward the basement fireboxes.

After six feet, the line went taut with a dull, wet thud.

It didn't bounce off brick or lodge against an iron damper flap. The weight sank into something soft, dense, and yielding, then stopped entirely. A sluggish bubbling sound drifted up the dark flue, like hot syrup boiling in a covered kettle.

I gave the rope a sharp yank. The lead plum didn't budge.

"Master?" Lázaro murmured from behind me. "Did it catch on an old soot shelf?"

"Soot shelves don't hold ten pounds of iron when you drop it from two yards up," I said.

I set both boots against the crumbling mortar of the rim, wrapped the hemp twice around my left forearm, and hauled back with my whole back. The rope groaned. Deep inside the shaft, something ripped with a sound like tearing canvas soaked in grease.

A foul puff of air blew straight up into my face. The stench was nauseating: sweet, rank, and blistering hot. It carried a fine dusting of yellowish ash that stung my cheek like needle points.

With a final heave, I ripped the iron plum free and hauled it to the daylight.

Lázaro leaned in, then recoiled, his hand flying to the brine nozzle slung at his hip. "Sweet mercy of the saints."

The lead weight was coated in a thick, fibrous black sludge that bubbled and hissed as the cooler air touched it. It was not creosote. The strands were thick as violin strings, woven in overlapping spiral lattices that gleamed with an oily, iridescent sheen. Trapped within the tangled fibers hung a charred strip of stiff leather. At the center of the leather was a small brass buckle, stamped with the mark of a local dairy. A handful of ginger fur clung to the charred buckle, half-digested and calcified into brittle glass.

Old Mistress Varo's ratter cat from the second floor. She had spent the last two days calling for it along the stairwells.

"Chitin," I muttered, scraping the edge of my thumb across the hardened edge of the web. The fiber resisted the edge of my utility knife, then cracked like tempered horn. "Fresh-spun. Within the last six hours."

Lázaro's face went pale under the layer of grime. "An Ash-Weaver? In a tenement chimney? Master, they only nest in the high-pressure gas conduits near the smelter yards. There's too much foot traffic here."

"A weaver doesn't care about foot traffic if the chimney drafts heat," I said grimly. I wiped the fouled blade of my knife on the slate. "Look at the webbing. It isn't just blocking the flue. It's drinking from it. Trilla has a leaking coal-gas pipe running right alongside this masonry core. The beast cracked the mortar to tap the gas line. It's feeding on the raw fuel and weaving the exhaust shut to build an incubator."

"If the gas pocket catches behind that plug—"

"The whole four stories blow out into the street," I finished for him. "And fifty poor bastards burn in their beds before they smell the sulfur."

I looked down at the twin-tank rig strapped to Lázaro's shoulders. The copper cylinders held four gallons of pressurized salt-brine and winter-oil foam, built by Inéz in the lower foundry cellars. At three bars of pressure, a single blast could drop the surface temperature of living iron by a hundred degrees in three seconds. Against an Ash-Weaver's glowing carapace, it was the only weapon that kept a sweep from being roasted in his own skin.

"Check the pressure gauge," I commanded.

"Three bars, steady," the boy replied. His voice shook slightly, but he didn't step back from the edge. "Do we call the Ward Dampeners? Baron Morillo's patrol is posted at the iron bridge."

I let out a harsh, dry bark of laughter. "The Iron Baron doesn't send his white-coated dandies into tenement crawlspaces for six copper groats, boy. Morillo would order the building barricaded, open the main district valve, and burn the whole block to slag to save his silver oxygen filters. We clear it ourselves. Or we don't eat tomorrow."

I reached for my heavy harness and the long steel scraper pole. We had our answer: the blockage wasn't soot, and it wasn't dead birds. It was an active nest. A nest meant meat, eggs, and an aggressive guardian defending its fuel source.

Before I could lock my carabiner to the flue anchor, the brickwork beneath my boots vibrated.

It wasn't the regular hum of the municipal pressure lines. It was a sharp, rhythmic scratching from deep within the chimney stack, rising at terrifying speed. Then, through the hot dark of the masonry, a sound tore outward: a shrill, chittering shriek that rattled the loose mortar and made the chimney cap ring like struck iron.

Down in the dark, four floors below, something had smelled the draft. And it was climbing.