Rerouting the Steam

The iron crawlway smelled of rotten eggs and scorched lard, and every joint in the casing was beginning to weep dirty condensate down my neck. If the basement boiler was still firing hard enough to send grease boiling through the overflow vents, then the lower junction was already running hot enough to cook our brine tanks into shrapnel before we ever reached the floor. I crouched on the rusted ledge above the drop, bracing my knees against the ribbed plates, and gripped the four-foot municipal wrench with both hands.

"Check the brass gauge on my shoulder harness, Lázaro," I said, keeping my head low beneath the hanging soot-ropes. "Give me the reading before the sweat blinds you."

Lázaro wiped his sleeve across his brow, leaving a black smear across his temples. He leaned close and squinted at the iron tanks strapped to my shoulders.

"One point nine bars, Master Mateiro," he croaked, coughing into his fist. The cough sounded wet, rattling in his throat like dry peas in a tin mug. "The seal is holding, but the casing is hot enough to blister grease."

"Keep the damp rag wrapped around the valve stem," I told him. "If the brine boils in the jacket, the pressure will blow the check plate right through your ribs, and I have no desire to sweep up your teeth with my hearth broom."

He nodded once, ducking his chin into his collar. Below our iron grate, the drop vanished into a cavernous basement junction. A spiderweb of secondary heating ducts branched off like severed arteries, burrowing into the plaster walls of the lower tenements. Every single branch was lined with thick, gummy layers of black pitch. Ash-Weavers didn't burrow through solid granite when they could commandeer a six-inch exhaust pipe. They had hollowed out the floor cavities between the flats, turning the building's heat grid into their private hunting runs.

I dropped down three feet to the boiler intake platform, my copper-plated boot heels clanging against the diamond plate. The air down here sat greasy and stagnant, so thick with vapor that my tongue tasted like boiled copper pennies.

To our left, three six-inch steam risers ran parallel to the main coal-gas intake, carrying low-pressure steam from the central boiler up toward the parlor radiators on the first floor. Or rather, they were supposed to carry low-pressure steam. Someone had hammered iron wedges into the emergency bypass shuttles, locking them halfway open.

"Look at the mortar around the floor grates," Lázaro whispered, lowering his soot-lantern. His hand trembled just enough to throw jittery yellow rings across the iron. "Those holes go straight into the baseboards."

I leaned over the curb of the nearest riser. Inside the six-inch opening, the pitch was fresh and glossy, steaming faintly in the updraft. Thin, fibrous strands of black silk stretched across the iron mouth, vibrating to an irregular rhythm deep in the masonry. Small feeding tunnels branched off into the walls, radiating into the rooms where the landlord's tenants slept. If we climbed down to the main boiler floor without sealing those runs, half a dozen flanking scouts could scuttle out behind us and drop onto our necks while we faced the flue.

I adjusted my grip on the municipal wrench, resting its hexagonal jaws against my boot. The weight of the four-foot iron bar pulled at the blisters on my palms, but the municipal hex matched the massive hexagonal stem on the main boiler return valve perfectly.

"You're closing the radiator loop?" Lázaro asked.

"Closing it sends the steam back into the cellar," I said. "We want the steam in the walls. We divert the whole header into the perimeter crawlways. The scum upstairs paid their rent for winter heat; let them enjoy floorboards hot enough to bake corn cakes."

I hooked the jaws of the four-foot wrench over the hexagonal stem of the master diversion gate. The municipal seal was cracked, the red lead paint flaking off under the teeth of the tool. I set my boots against the boiler footing, bent my back, and hauled down with my full weight.

The valve screamed. Rusted threads ground together inside the bronze housing with a shriek that sounded like iron teeth on glass. Flakes of orange scale cascaded over my sleeves. The stem gave half an inch, shuddered, and then seized tight.

"Put your weight on the bar," I grunted. "Don't stare at it. Pull."

Lázaro lunged forward, throwing his small frame over the end of the handle. Together, our combined weight snapped the frozen threads free. The wheel rotated a quarter turn, then another, until the bronze gate slid down into the channel with a heavy, hollow thud.

Instantly, the pitch of the basement changed.

The wet hissing of the central draft died away, replaced by a hollow, subterranean roar. Behind the brick bulkhead, hundreds of gallons of superheated steam, cut off from the residential risers, slammed directly into the low-pressure wall flues. The pipes shuddered so violently that flakes of whitewash rained from the ceiling joists.

A terrible, muffled screech erupted from inside the floorboards.

Through the nearest six-inch iron vent, a blast of scalding vapor erupted like the spout of a breaching whale. The glossy pitch lining the pipe didn't burn; it curdled. It shriveled into gray ash under the blinding cloud of damp heat. Inside the crawlspace, thrashing legs clicked furiously against the lath and plaster. Two scout weavers, caught in the sudden rush of boiling fog, tumbled out of a floor opening, their black carapaces peeling and smoking as the steam cooked their joints into chalky ruin. They hit the stone floor twitching, their segmented legs curling inward like burnt bristles.

"It works," Lázaro breathed, raising the lantern. "The runs are drowning."

"They're drowning, but the cast iron isn't built for three atmospheres," I said, eyes fixed on the manifold junction above our heads.

The small brass pressure gauge mounted on the header was vibrating so hard the glass face had cracked down the center. Its blackened needle had surged past the green marks, swung through the yellow caution band, and now pressed hard against the brass peg at the red limit. Thin whistles of white steam began spitting from the solder collars along the main drum.

We had sealed off their escape routes and purged our flanks, but we had turned the building's cast-iron heart into a kettle with the lid bolted down.

I wiped the condensation from my chin, feeling the wet heat press against my temples. The steam had boiled out the secondary channels, yet the boiler below was still being stoked by whatever horror nested in the firebox.

"Keep hold of the hex-wrench, Lázaro," I said, letting him take the bar as I stepped toward the iron ladder that dropped through the cellar floor. "The boiler isn't going to wait for us to find a tea cup."