The Scrubber Rat of Venus

• Chapter 1 Below the Spire
• Chapter 2 Acid Rain on the Glass
• Chapter 3 The Crawlspace Guild
• Chapter 4 Filter Teeth
• Chapter 5 Yellow Mist Rising
• Chapter 6 The Smallest Hands
• Chapter 7 Rust and Rhythm
• Chapter 8 Poison in the Ducts
• Chapter 9 The Cloud-Skin Breach
• Chapter 10 Valve Forty-Nine
• Chapter 11 A Pocketful of Gaskets
• Chapter 12 Ghost in the Flue
• Chapter 13 The Upper Promenade
• Chapter 14 Stolen Oxygen
• Chapter 15 Burn Marks and Brine
• Chapter 16 The Shifting Vent
• Chapter 17 Sulfur Blindness
• Chapter 18 Children of the Core
• Chapter 19 Pressure Drop
• Chapter 20 Whispers Through the Mesh
• Chapter 21 The Great Condenser
• Chapter 22 Sabotage in Sector Six
• Chapter 23 The Weight of Breathing
• Chapter 24 Into the Sulfuric Dark
• Chapter 25 Turning the Main Turbine
• Chapter 26 The Clear Sky Above

The grease on Venus did not smell like animal fat, because there were no pigs floating fifty kilometers above the basalt crust, only six hundred thousand people suspended inside giant inflated blisters of fluoropolymer. It smelled instead of tallow mixed with pulverized zinc and the bitter, cabbagey tang of recycled nitrogen. When it got hot enough inside the conduit casings, it smelled like fried hair.

Milo was ten, which meant his clavicles still had enough give to let him slip through an eighteen-inch inspection hatch without dislocating his shoulders, provided he exhaled first and kept his arms pinned straight ahead like a diver entering cold grease. If he grew another half-inch before the autumn intake, he would be reassigned to the sump rakes down on Deck Thirty, where the air was wet and yellow and people lost their teeth before their sixteenth birthdays. For now, he was a rat, and the bore was his kingdom.

"Heels up, Milo," Master Varos barked from the access staging. Varos was sixty, an impossible age for the air-works, and possessed of two brass fingers on his left hand to replace the ones sheared off by an oscillating damper valve back when the aerostat was still called New Antwerp. "You're dragging your boots on the sensor leads. Those wires cost more than your funeral, and your funeral is paid out of my pocket."

"My boots are up, Master," Milo called back, his voice flat and deadened by the acoustic foam lining the cylinder. He was wedged four feet into the dark, his chin resting against a cross-brace that hummed with sixty-cycle vibration. "There's scale on the secondary rotor. Thick as grease-cake."

"Don't tell me what it looks like, scrape it off," Varos rasped. "The upper promenade is pulling thirty-two parts per million of sulfur dioxide since the third bell. The Councilors are coughing into their silk napkins. If their tea tastes like rotten eggs at noon, the Overseer cuts our meal tickets by half."

Milo produced his scraper—a strip of hardened leaf-spring steel with one edge ground down to a chisel point—and began to work on the cake.

The conduit was designated Return Line 4-B, a lateral arterial that pulled stagnant air from the underbelly of the residential tiers, dragged it through the electrostatic precipitators, and shoved it back up into the grand atrium where the brass fountains ran day and night. The brass fountains did not spray water; water was too precious to splash about for the amusement of administrative clerks and their high-collared wives. They sprayed chilled paraffin oil that had been dyed pale blue, which looked enough like water from ten yards away to keep the population from going completely mad with claustrophobia.

The scale came away in brittle, grayish curls that fell against Milo’s chest like dry scabs. It tasted sour on the back of his teeth, a sharp, metallic bite that no amount of mouth-rinsing with chalk-wash ever entirely removed. Every child who worked the tubes had that taste. They called it the penny-tongue. If you woke up in the barracks and your mouth didn't taste like an old copper washer, you were probably dead, or worse, your sector had run out of buffer salts and the main envelope was beginning to rot from the inside out.

He dragged himself forward two inches on his elbows, feeling the rough hemp of his dungarees catch against the rivet heads. The ventilation tube wasn't round; it was an irregular flattened oval, pinched where the load-bearing stays of the exterior trusswork passed through the deck floor. That was the real problem with the aerostat St. Jude. When the engineers had laid out the plans in the dry docks of Luna fifty years ago, they had forgotten that a mile-wide sphere of gas bags and titanium struts twists when a gale blows off the equator. The city had flexed, the girders had settled, and the clean, round maintenance ducts had crumpled into crooked intestines that no mechanical brush could navigate. Machines got stuck. Adults didn't fit. Only a boy with thin ribs and empty pockets could reach the deposits before they choked the air thin.

"Clear the throat-ring first," Varos called up the hole. His voice sounded farther away now, muffled by the rising gale outside the hull. "The wind is veering south-southwest. The clouds are stacking up against the belly-plates."

Milo felt it in his shins before he heard it—a deep, shuddering groan that traveled through the titanium ribs of the city. Fifty miles below them, the true surface of Venus lay under ninety atmospheres of carbon dioxide so hot it could melt lead like butter on a griddle, but up here, at fifty-two kilometers, the pressure was one bar, the temperature was twenty degrees Celsius, and the only thing trying to kill you was the sulfuric acid mist that blew at two hundred miles an hour against the skin of the world.

A sudden downdraft struck the exterior cowls. Through the thin sheet-metal of the conduit, Milo heard the hiss—the terrible, wet slap of acid spray hitting the neutralizing jackets. It sounded like grease hitting a hot skillet, magnified a thousand times over, a sizzling roar that drowned out the hum of the turbines.

He didn't pause his scraper. If you stopped working every time the clouds spit on the ship, you’d spend your whole shift shaking in the access wells.

"Rotor's loose, Master," Milo said, leaning his forehead against the damp metal to reach the hub nuts with his small box-wrench.

"How loose?"

"Two threads. The locking cotter has rusted out. Nothing left but the head."

"Cotters don't rust out in four days," Varos grumbled, his knuckles rapping hard against the exterior of the pipe, three feet below Milo's knees. "They're nickel-plated."

"This one didn't get the nickel, then," Milo muttered. He worked the wrench by feel, his fingers numb from the constant draft that whistled past the seals. "It’s pitted right through. I can flick it away with my thumbnail."

He did so. A tiny flake of black iron fell into his shirt collar, stinging the skin of his neck where the sweat had softened it. The acid got in everywhere, carried on the damp breath of three generations of people who had never set foot on dry dirt. It rode their clothes, it lived in their hair, it ate the brass buttons off their jackets until they were forced to use wooden pegs to keep their coats shut.

The bolt was stiff, frozen by a greenish crust of copper sulfate that had migrated from the motor housing. Milo braced his heels against the casing wall, took a breath so deep his ribs pressed hard against the steel above him, and threw his weight into the turn.

The wrench slipped.

His knuckles cracked violently into the sharp edge of the damper bracket. Milo didn't yell; yelling in the tube wasted air and filled your mouth with the gray silt you’d just spent twenty minutes loosening. He simply closed his eyes, pulled his hand back to his chest, and sucked the blood off his split skin. It tasted hot and clean, completely different from the air-works, which tasted like things that had died three months ago in an old bucket.

"Milo?" Varos’s voice was sharper now. "You drop that spanner?"

"No, Master."

"Keep a grip on it. If you drop a four-ounce tool down the intake throat, it’ll chew through the secondary impellers like dry biscuits. Then we’re both on the scrap gang by third shift."

"I have it," Milo said. He took the tool back into his right hand, ignoring the dull, throbbing heat in his index finger. He set the jaw against the flats again, positioned his body slightly differently, and brought the heel of his left hand down sharply against the wrench handle.

The nut gave with a screech that set his teeth on edge.

He spun it off, wiped the threads with a mouthful of spit on a rag, and fished a fresh cotter pin from the leather pouch tied to his ankle. Working blind with two fingers, he guided the thin wire through the hole in the bolt-shank, spread the legs with the flat of his chisel, and bent them back until they hugged the nut. It was clumsy work, the kind of job an apprentice on Earth would have been thrashed for doing so poorly, but down here on the forty-fifth level, fifty yards from the outer envelope, "good enough to spin" was the only standard that mattered. If it spun for forty-eight hours without seizing, the shift was a success.

He reached for the next rotor blade.

This one was different. It wasn't just scaled with the usual lime-colored grease; something had jammed itself into the clearance gap between the blade tip and the inner sleeve. It was small, no larger than a plum, wrapped tightly in oilcloth and lashed to the housing with three turns of copper safety wire.

Milo stayed very still. The air whistling past his ears seemed to drop an octave as the turbine load shifted somewhere down the line.

You didn't find packages in the ducts. You found dead rats—the four-legged kind that came off the grain transports from Callisto twenty years ago and had evolved hairless skins and stunted ears—and you found dropped nuts, broken drill bits, and occasionally a child’s shoe that had slipped through an intake grille during the cleaning cycle. You didn't find oilcloth wrapped with wire.

"What's the delay, boy?" Varos's boots shifted on the iron staging below. "You're thirty minutes into the watch and I haven't heard the blower turn over."

"Scale was thick on the backside," Milo said, his voice coming out louder than he intended. The lie was automatic. Every child in the lower tiers learned to lie before they learned their letters; letters only got you into trouble with the tax-clerks, but a good lie could save your crust for the evening. "I'm clearing the shroud now."

He worked the wire loose with his scraper point. It wasn't the standard copper wire the maintenance division used; this was thin, single-strand stuff, the kind used to bind the paper insulation on the main telegraph circuits that ran up through the central core to the Governor's spire.

The oilcloth was greasy, stiff with cold, and smelled sharply of turpentine. He tucked it into the deep breast pocket of his dungarees, beneath his undershirt, where it sat cold and square against his ribs, right over his heart.

"All clear on the rotor," Milo called out, his lungs working hard. He didn't like the feel of the bundle. It had corners. Sharp, hard corners that felt like brass.

"Back out, then," the master said. "The mid-day purge is coming through in ten minutes. If you're still in the pipe when they blow the nitrogen lines, they'll be sweeping your lungs out of the lower collectors with a hair broom."

Milo didn't need to be told twice. Backing out of an eighteen-inch line was an art distinct from going in. Going in was mostly about sliding and letting gravity do the dirty work as the duct slanted downward toward the exterior ring. Coming out meant using your toes to find the seams in the metal, digging your fingernails into the rust-pockets, and inching backward like an earthworm caught in a downspout.

His knees scraped through the patches on his trousers. The fabric had worn away three weeks ago, and the skin beneath was a patchwork of gray calluses and pink, half-healed scabs from the raw rivet edges. He kept his head down, chin tucked against his breastbone, eyes shut against the fine, stinging dust his heels kicked up with every hitch.

Five feet. Four feet.

The draft grew stronger, smelling of Varos's sour pipe-weed and the damp floor of the maintenance bay. A pair of large, leather-gloved hands reached into the pipe, grabbed Milo by the ankles, and hauled him out with two rough, efficient jerks that left his hips bruised against the hatch coaming.

Milo hit the iron grating of the staging on his side, curling into a ball out of habit until he was sure he wasn't going to roll over the edge.

"Get up," Varos said, not looking at him. The old man was already busy wiping his wrench with an oily rag, his brass fingers clicking against the steel like knitting needles. "You look like a chimney sweep from an old book. Drink your tea."

A tin mug sat on the tool chest, steam rising from its surface in a faint, grayish wisp. It wasn't tea, of course; it was boiled water flavored with chicory and salted with the magnesium cakes they handed out to keep the workers' muscles from knotting up into hard, agonizing balls. Milo took the mug with both hands, his fingers trembling with the relief of being straight again. His backbone felt like a dry rope that had been pulled tight and left in the sun.

He drank. The salt burned the raw spot on his knuckle, but it chased the sulfur taste out of his throat, down into his belly where it churned with the bread he’d eaten six hours ago.

"Look at the pressure gauge," Varos said, nodding his chin toward the brass-rimmed dial mounted on the bulkhead.

The black needle was trembling just inside the red zone—twenty-eight pounds per square inch over ambient. The glass was clouded with a film of pale green corrosion around the bezel, but the red line was clear enough.

"They're pushing the blowers too hard," Milo said, his teeth clicking against the rim of the tin cup.

"They're pushing them because Tier Two is having a ball tonight," Varos spat into the drainage channel between his boots. The spit bubbled briefly against the iron before vanishing into the sump. "The high-ups are celebrating the anniversary of the First Anchorage. Sixty years of floating over the furnace without the floor burning through. They want the air sweet as lilac water for the dancers. So we burn the rotors, and you scrape the carbon until your elbows leak water, and the Governor drinks white wine from Earth that costs more than this whole deck would fetch if you sold it for scrap to the orbital yards."

Milo didn't answer. He set the mug down and felt his chest through the heavy canvas of his bib. The package was still there, sitting flat against his skin. It had warmed up from his body heat, and now the smell of the turpentine was coming through the weave of his shirt, sharp and unnatural.

"What's that smell?" Varos asked, his single eye narrowing as he turned back from the valve tree. His other eye was clouded over, white as a boiled egg, the result of an ammonia leak thirty years ago.

"Solvent," Milo said instantly. "From the rotor hub. Someone dumped degreaser down the vent from Deck Twenty."

Varos grunted, satisfied with the explanation. "Fools. They think because it runs down, it disappears. Everything in this basket comes back around. You dump it down, it comes up your nose six hours later. You’d think an engineer would understand how a circle works, but they don't teach them that in the academies on the Moon. They just teach them how to draw straight lines with silver pencils."

The old man gathered his kit—three wrenches, a copper mallet, and a wooden box of replacement seals—and dropped them into his canvas bag with a series of dull clanks.

"Take the lift up to Sector Nine," Varos said, wiping his nose with the back of his leather sleeve. "Check in with the intake foreman. Tell him 4-B is turning clear, but the bearings are singing high C. If he doesn't drop the load before third bell, he’ll have three hundred pounds of copper bird's-nest in his rotor box."

"Yes, Master."

"And wash your face at the trough. You look like an off-worlder's boots."

Milo waited until the master’s heavy, uneven tread had died away down the service walkway. The walkway was made of perforated sheet iron, through which one could look down into the dim, misty depths of the lower helium cells. Down there, hundreds of feet below the living quarters, the light was always a sickly amber, filtered through thousands of yards of semi-transparent skin that kept the city from dropping into the crushing heat of the Venusian deep. Milo never looked down through the holes if he could help it. It wasn't the drop that bothered him; it was the realization of how thin the iron was, how thin the gas-skin was, how little there was between his boots and the great yellow mouth of the planet below.

He ducked behind the casing of Return Line 4-B, into the crawlway between the air-shaft and the structural skin of the interior bulkhead. It was dark here, lit only by the occasional spark from an overhead trolley line that ran along the ceiling.

He pulled the package from his shirt.

The oilcloth was thick—military issue, the kind they used to wrap hydraulic spares for the attitude thrusters. It was sealed with reddish wax that had been pressed with a thumb-mark, though the print was smeared beyond recognition.

Milo used his thumbnail to pry at the corner of the wax. It came away in dry, crumbly flakes that fell between the floor-ribs.

Inside the cloth was a notebook. Its cover was made of thin, pressed zinc—waterproof and acid-resistant—hinged with small brass rings that had been hammered flat with a punch. The pages weren't paper; paper was too rare on the aerostats to waste on notes. They were thin sheets of white vinyl, the surface roughened so it could take a pencil lead.

Milo flipped the cover open.

He couldn't read the words—the letters were small, cramped, and written in the rapid, slanted hand of someone who had never had to carve their alphabet into lead tags with a scriber—but he knew what the drawings were.

They were cross-sections of the Spire.

Not the decorative diagrams they had pinned up in the schoolrooms on Deck Twelve, showing the aerostat as a great silver lotus floating peacefully above the clouds, with flags flying from the radio masts and little arrows showing how the clean air went in and the bad air went out. These were real drawings. They showed the high-pressure steam mains, the hydraulic lines for the stabilization fins, and, most clearly of all, the great primary vents—the massive, five-meter tubes that carried the hot, compressed air from the belly-rams directly into the Governor’s personal gardens at the tip of the spire.

One of the drawings had a red line drawn through it.

The red line started at Return Line 4-B, where Milo had just been lying with his knees in his armpits. It ran straight through the intermediate filtration boxes, bypassed the charcoal banks entirely, and entered the intake for the Grand Council Chamber through the decorative gilt grilles beneath the speaker’s chair.

Beside the line, written three times in heavy, dark pencil, was a single number: 49.

A sudden hiss of escaping steam made Milo jump, his head striking the underside of an oil pipe with a sharp metallic thunk.

He tucked the zinc book back into its oilcloth, wrapped the single strand of copper wire around it three times, and shoved it deep into the bottom of his pocket, beneath his spare gaskets, his box-wrench, and the handful of lead washers he had scavenged from the staging floor.

Above him, the sirens began to wail for the mid-day purge.

It was a low, mournful sound, like a cow dying in a bog, that echoed through every tube, conduit, and living compartment in St. Jude. In thirty seconds, the automatic valves would slam shut with the force of guillotine blades, and twenty tons of pure, bone-dry nitrogen would blast through the return line at three hundred miles an hour to scour the dampness from the walls.

If he had been three minutes slower with that cotter pin, he would have been turned into pink spray against the primary intake screen.

Milo scrambled out of the crawlway, his boots slipping on the slick iron of the staging. He didn't head for Sector Nine. He didn't want to see the intake foreman, and he certainly didn't want to explain why his knuckles were bleeding and why he smelled like turpentine instead of standard-issue lard.

Instead, he took the narrow ladder that clung to the exterior of the central spine, climbing up toward the light, away from the hum of the turbines and the stink of the acid-pots.

As he climbed, he could hear the music starting on the upper levels. It was thin and tinny, carried down through the ventilation ducts by the forced draft—the sound of fiddles and a small, mechanical organ that played the same waltz every time the Governor held an audience. The people up there were putting on their shoes—real leather shoes that had never been soaked in vinegar to keep the mold from eating them—and their daughters were pinning paper flowers into their hair.

Milo reached the landing for Deck Thirty-Eight.

Here, the air was slightly cooler, though it had that sour, second-hand quality that came from passing through fifty sets of lungs before it reached the vents. A gang of older boys—sweepers who had grown too broad across the hips to work the four-inch pipes—were sitting on a stack of collapsed gas bags, playing knucklebones with sheep joints they’d stolen from the galley chutes.

They looked at him as he came off the ladder, their eyes dull and watery from the constant drafts.

"Hey, Scrubber," one of them called out. He was twelve, with the long, thin neck and sloping shoulders of a boy who was growing faster than his rations could keep up with. "Varos is looking for you. He says you left your grease-tin behind."

"It's in my bag," Milo said, not stopping.

"He says the Council chamber's got the stink again," the boy shouted after him, laughing with a wet, rattling sound in his chest. "They say it smells like something crawled into the flue and died. Maybe it was your brother."

Milo kept his hands in his pockets, his fingers curled tight around the cold, zinc edges of the notebook. He didn't have a brother. Nobody on Deck Thirty-Eight had a brother for long; if the croup didn't take them before their second year, the dry-rot did, or they simply disappeared into one of the vertical shafts when their grip failed on an oily rung.

He turned into the narrow alleyway that led toward the living blocks of the Crawlspace Guild. The walls were made of corrugated iron that had been painted so many times with green zinc-chromate that the rivet heads looked like big, smooth peas under the skin of paint. The air smelled of boiled lentils and the pungent, vinegar steam from the laundry vats where the women tried to wash the yellow stains out of the work-shirts.

He reached his own hatchway—Number 404, a square hole three feet off the deck, covered with a flap of greasy canvas instead of a door.

Inside, the bunk was six feet wide and five feet deep, built directly over the secondary exhaust trunk for the tier's communal latrines. It was warm, at least. The metal beneath the thin straw pallet never cooled down below thirty degrees, though on bad days, when the wind came around from the west, the smell through the welds was enough to make your eyes water until you couldn't see the ceiling.

Milo crawled in, let the canvas flap fall, and sat in the dark.

The aerostat tilted slightly, three degrees to the leeward, as a heavy squall caught the upper gas envelopes. In the distance, through miles of pipe and structural steel, he heard the dull, metallic thud-thud-thud of the balancing pumps shifting five thousand gallons of brine from the port tanks to the starboard to keep the floor level. It was the rhythm of his life, the only heartbeat the city had—the pumps, the blowers, the hiss of the spray, and the eternal, faint whistle of the outside air trying to find a hole small enough to get in and burn them all down to their teeth.

He took the book out and laid it on his knees.

Even in the pitch dark, he could feel the shape of it. It was too clean, too sharp, too well-made to belong down here with the grease-rats and the scrapers. It belonged up in the Spire, where the brass was polished until you could see your face in it, and the ladies didn't have gray rings around their necks from their collar-bands.

He ran his thumb over the zinc cover until he found the corner he had bent back.

Under the flap of the oilcloth, his fingers found something else he hadn't noticed while he was shivering on the staging below Return Line 4-B.

It was a key.

Not an iron key like the ones Varos carried for the tool-cribs, or a notched piece of brass like the ones that opened the locker-latches in the barracks. It was small, triangular, made of some heavy, dark metal that didn't smell like rust or grease, and on the bow of it, cut into the metal with three neat strokes of a diamond drill, was the number 49.

Milo tucked the key into his sock, pulled the straw pallet up to his chin, and listened to the air whistling through the rivets. The mid-day purge was over, and the turbines were beginning to wind back up, their low, familiar hum rising through the deck plates until it rattled the fillings in his teeth.

The air was coming through the pipes again—thin, salty, and cold, straight from the clouds, carrying just enough life to keep six hundred thousand people from noticing that they were all drowning in their own breath.

The nearest outer port on Deck Thirty-Eight was set into the recess of an auxiliary pump station called the Lantern. It wasn’t an actual window in any civilian sense; nobody on the lower decks was permitted to loiter beside the exterior skin for the sheer pleasure of looking at yellow fog. It was an inspection blister, three inches of laminated quartz glass clamped inside an iron ring that had been bolted through the aerostat's secondary vulcanized hull. Every apprentice knew the spot because the drainage gutters from the water recyclers ran right beneath the floor grating, making it the only place on the deck where you could wash your forearms without getting shouted at by a boiler tender.

Milo stood on his toes, his thumbs hooked in the frayed straps of his dungarees, and pressed his cheek against the cold brass collar of the frame.

Outside, the atmosphere was doing its usual work of trying to dissolve the world. The clouds here were not the fluffy white heaps people painted on the ceiling medallions in the Upper Promenade, but a thick, soupy emulsion of sulfuric acid and superheated steam that raced past the hull like dirty river water. It came in horizontal sheets, slamming against the curved quartz with a wet, abrasive rattle like handfuls of coarse salt hurled against a drumhead. Every few seconds, a heavier smear of pale, curdled yellow would hit the glass, flatten out into greasy streaks, and then be ripped away into the void by the two-hundred-mile-an-hour headwind.

Below the glass, the great belly-plates of the aerostat were barely visible, their heavy coats of black fluorocarbon enamel pitted and scarred by decades of continuous chemical scrub. Through the murk, about forty feet down, Milo could see the run-off channels. They were glowing faintly with the greenish phosphor-wash the deck crews painted along the weld seams to check for structural stress. Whenever the aerostat flexed in a heavy thermal gust, the seams gave off a tiny, shivering blink of emerald light, like a long row of sleepy eyes winking deep under the mist.

"It’ll eat through your goggles if you keep staring like that, rat," a voice said behind him.

Milo didn’t jump, though his left heel twitched against the floorplates, right where the triangular key was tucked into the tight weave of his woolen sock. He turned slowly, keeping his back half-pressed to the iron bulkhead.

The girl leaning against the drainage casing was thirteen, maybe fourteen, though she wasn't much taller than Milo. Her name was Vena, and she belonged to the external caulking shifts—the ones they strapped into leather slings and lowered out through the belly-locks with tallow tubs and pneumatic rivet guns whenever a storm tore the outer skirts loose. Her face had the distinct, mottled look of someone who worked the outside air: pale everywhere except for the sharp, reddish-brown freckles across the bridge of her nose and cheekbones where the acid vapors had seeped through the edges of her rubber breather mask. Her fingers were short, blunt, and stained an unshifting dark umber from the bitumen sealant they used on the exterior seams.

"It’s not eating anything," Milo said, wiping his nose with his wrist. "The glass is two inches thicker than your head."

"It’s three inches, and it gets four millimeters thinner every ten months," Vena replied matter-of-factly, stepping onto the iron grating. She carried an empty three-gallon galvanized bucket and a broad scraping blade with a hickory handle, worn smooth by greasy palms. "The depot master down on forty-two says if the Luna freighters don’t bring a fresh consignment of quartz blanks before the dry season, they’re going to plate over the Lantern entirely. Just bolt a steel blank over the bore and leave us with the kerosene lamps."

"They won't do that," Milo said. "The inspectors need to see the skirt-hinges."

"The inspectors don't look at the skirt-hinges with their eyes, idiot. They use the sonic thumper from the service trench. Nobody looks through the glass except grease-monkeys who haven't got enough sense to stay out of the draft." She dropped her bucket into the wash-sink with a loud clatter that made the copper pipes under the deck shudder. "Why aren't you with Varos? I saw him down at the intake junction twenty minutes ago, cursing so loud the soot was dropping out of the secondary flue. He said you were supposed to carry his report to the sector head."

Milo looked down at his boots. The leather around the toes was curled up like dried fish from too many cycles of wet steam and dry nitrogen purges. "The line was clear. I set the cotter pin."

"He said you took forty minutes on an eighteen-inch bypass." She turned the brass petcock over the trough. A thin, sputtering stream of grayish water came out, smelling sharply of limestone and sulfur. She shoved her hands into the stream, not flinching at the heat, and began to work the dark bitumen grease from the creases of her knuckles with a bar of harsh pumice soap. "Old man thought you'd got your ribs caught in the damper bracket. He had the pry-bar out and everything."

"I was clearing scale," Milo said. He kept his hands deep in his dungaree pockets, his fingers curled around the zinc notebook. The weight of it against his hip felt massive, as if the metal pages were cast from lead instead of thin sheet. "The rotor had grease-scabs the size of dinner plates. A lot of it."

Vena shot him a sideways look through a tangle of dark, matted hair that had escaped her canvas work-cap. Her grey eyes were sharp, missing very little that happened within five feet of her boots. Working the caulking slings taught people to notice things quickly, mostly because hesitation usually ended with a frayed lanyard and a three-mile fall through eighty atmospheres of boiling gas.

"You're twitching, Milo," she said, scrubbing the soap over her forearms until the skin was pink and raw. "You only twitch like that when you've pinched something from the engineering stores. What did you get? Another brass grease-cup? Because if it’s a grease-cup, the quartermaster has already counted the inventory on Tier Thirty-Nine, and he’s docking the whole apprentice crib two ounces of bread tomorrow morning."

"I didn't pinch anything from the stores," Milo said, his voice flat. It was technically true. He hadn't touched the quartermaster's grease-cups.

"Then you found something in the trunk." She rinsed her hands, shook the drops off into the scum-basin, and wiped her palms down the legs of her duck trousers. She didn't look at him when she spoke next, lowering her voice so that it barely carried over the steady, hollow hiss of the gale against the inspection glass. "Was it from above or below?"

Milo took half a step away from the window frame, glancing toward the service ladder that dropped down to the lower catwalks. The passage was empty, save for a line of hanging canvas fire-hoses and the dim, red-glowing elements of the humidity traps mounted every thirty feet along the iron ceiling.

"What do you mean?" he asked.

"You know what I mean. The purge sirens went off twelve minutes early on forty-four. They didn't blow nitrogen from the central reservoirs; they pulled it off the main ballast banks. That means someone in the high administrative blocks wanted the lines cleared in a hurry, or somebody tripped a secondary sensor between here and the Spire." She leaned against the edge of the wash-trough, crossing her arms over her chest. "They don't dump ballast gas for fun, Milo. That stuff costs twelve hours of turbine-coal to compress back into the cells."

The wind outside took another violent bite at the Lantern. The thick laminated quartz gave a tiny, dry squeak against its lead mounting ring as the aerostat tilted through five degrees of roll. High above their heads, deep inside the structural gut of the ship, the great steel suspension cables groaned—a sound like a cello string the size of a pine tree being pulled until the resin smoked.

Milo pulled the oilcloth bundle half an inch out of his pocket, just far enough for Vena to see the reddish-brown edge of the sealing wax, before shoving it back down until his knuckle hit the seam.

Her mouth didn't drop open, but her eyebrows came together until the freckles on her nose formed a single dark line.

"Where was it?" she whispered.

"Behind the secondary rotor on 4-B," Milo said, keeping his eyes on her boots. "Tied off to the casing with telegraph wire. Copper strand, single-core."

"Did Varos see it?"

"No."

"Did you show it to the intake foreman?"

"I didn't go to Sector Nine," Milo said. "I came straight up the service rib."

Vena stood away from the trough, her movements deliberate and quiet. She reached out with one wet finger and jabbed Milo hard in the center of his chest, right where the zinc cover sat beneath his shirt. "You're a monumental fool, Milo. You know what happens to rats who find things in the high-pressure runs? They don't put them on the scrap gangs. They don't even throw them out the lock. They put them in the sulfur kilns down on Deck Fifty-Two, where the fire-tenders lose their eyes by twenty and their lungs turn to yellow porridge before their hair comes in."

"It has drawings," Milo said, ignoring the jab. "Drawings of the primary vents. The five-meter ones that feed the high rooms."

"I don't care if it has drawings of the Governor’s grandmother with no skirts on," she hissed, her voice cutting sharp through the rumble of the rain outside. "You put it down a grease-shoot. You put it down right now, pull the valve, and let it go into the main sludge digester. By the time it hits the acid pans at the bottom of the hull, it won't be anything but grease and soot, and you’ll still have all your teeth."

"There was a key," Milo said.

That made her stop. She had been reaching for the handle of her galvanized bucket, ready to push past him toward the crew mess, but her hand froze an inch above the iron wire bail.

"What kind of key?"

"Heavy. Dark metal. Triangular shank with three holes in the bow." Milo shifted his weight, feeling the sharp corner of the thing pressing into his ankle-bone through his coarse sock. "It has forty-nine stamped on the side. Three times with a punch."

Vena didn't speak for nearly a minute. The only sound in the recess was the rhythmic, greasy slap of the acid sheets striking the quartz blister and the wet wheeze of the drainage pipe under their feet. Her eyes moved from his face to the round glass behind him, where the greenish phosphor of the hull seams was flickering like a dying torch in the thick amber mist.

"There aren't forty-nine levels on this aerostat," she said slowly.

"I know that," Milo said. "The keel ends at Forty-Six. Below that it’s just the ballast fins and the drainage sumps."

"The Spire has three levels of state apartments," she murmured, her gaze drifting back to the ceiling plates. "Then the council hall, then the grand conservatory, then the radio dome. That’s five. Forty-six and five is fifty-one."

"Forty-nine is the chamber floor," Milo said, remembering the diagram in the notebook. The thin red line, drawn with the careful, mechanical precision of an architect’s ruling pen, had split into three branches right beneath the speaker's dais. "Just under the intake grilles. The drawings showed a junction box between the secondary return and the main draft."

Vena picked up her bucket. She didn't drop it this time; she held it by the rim, her fingers pressing into the zinc until the knuckles turned white under the black streaks of bitumen.

"My brother worked the gas-skirt crew three years ago," she said, her voice so low Milo had to lean forward to hear it against the whistle of the exterior gale. "Before his lanyard snapped. He said the Councilors don't just vote on the meal tickets and the coal allocations. He said they’ve got a second set of controls up there. Emergency valves that can cut the air to any three sectors on the ship if there's a riot in the work-gangs."

"They wouldn't do that," Milo said automatically. "If they cut the air, the scrubbers choke. If the scrubbers choke, the whole tier rots."

"They don't care if Tier Thirty-Eight rots, you idiot," she said, her voice rising slightly before she caught herself and looked down the companionway. "They can seal the deck from the main riser, pump three tons of limestone dust down the central flue to neutralize the rot, and let it sit for two months until the smell goes off. Then they ship five hundred more orphans from the high-orbit stations on the next bulk freighter, hand them scrapers, and start over."

Milo thought about the small zinc pages. They hadn't shown limestone dust. They had shown high-pressure bypass lines, thin pipes that cut straight through the filters without touching a single cake of activated charcoal or a single tray of soda lime.

"The book isn't from a councilor," Milo said.

"How do you know that?"

"The handwriting is too fast. It looks like the scrip-notes the grease-masters write on the inventory boards when the shifts change. It’s got oil on the corners. Old oil, not the sweet paraffin they spray in the fountains."

Vena looked at him for another second, her face hard and set, then she turned toward the companionway. "Come on."

"Where?"

"Not here. The Lantern shift-boss comes through every half-hour to check the glass for acid-pitting. If he catches us standing in the recess with empty buckets, he’ll have us on the night-watch at the grease-traps."

She didn't wait to see if he was following. She stepped out into the main passage, her boots making a soft, sucking sound on the damp duck-boards that covered the iron deck. Milo hesitated for half a breath, his hand straying once more to the lump in his bib, then he fell in behind her, keeping his elbows tucked close to his sides to stop his tools from clinking in his pocket.

The main passage of Deck Thirty-Eight was eight feet wide, framed with curved ribs of rolled iron that had been salvaged from some older, failed aerostat fifty years ago. You could still see the numbers stamped into the iron near the rivet lines—NEW GLASGOW - LORNE SYSTEM - 2084—crossed out with three strokes of a cold chisel and over-stamped with the broad arrow of the St. Jude municipal works. Every ten yards, a low-wattage glow-bulb hung inside a thick wire cage, its yellow filament shivering with the constant, sixty-cycle pulse of the main steam turbines four hundred feet above their heads.

The air here was heavier than it had been in the Lantern. It had the thick, oily weight of human breath mixed with the steam from forty communal kitchens, all boiling the same grayish salt-beans over open electric plates. Groups of children were huddled in the small recesses between the ribs, some of them sleeping with their knees pulled up to their chins, others mending their leather shin-guards with strips of copper wire and split-rivets.

Nobody looked at Milo and Vena as they passed. On Thirty-Eight, looking at other people was an easy way to get drawn into an argument about soup-rations or who had stolen whose wrench from the shared drying-racks. Everyone kept their chins down, their eyes fixed on the seams in the deck-plates, listening to the rhythm of the city’s heart.

Thump-hiss. Thump-hiss.

It was the great low-pressure balance pump at the center of the sector, hauling sixty gallons of sour water out of the bilges with every stroke and shoving it toward the evaporators on Thirty-Five. When the pump stuttered, everyone stopped walking until it caught its rhythm again. If it stopped entirely, you had about forty minutes before the floors started to sweat cold grease, and an hour before the carbon dioxide built up thick enough along the gutters to make a grown man fall over on his face.

Vena led him past the entrance to the communal bunk-rooms, down a short, steep ramp that led toward the secondary filter bays. Here, the noise of the aerostat changed. The dull rumble of the wind against the skin was muffled by thousands of tons of machinery, replaced by the high, singing whine of the centrifugal fans.

They stopped at the foot of an access trunk marked with a circle of white lead paint: 4-B SECONDARY ACCELERATOR - CREW ONLY.

"Why did you bring me back here?" Milo asked, his mouth going dry. "Varos is probably down at the header."

"Varos is sixty years old and he’s got two brass fingers," Vena said, turning to face him in the narrow, green-lit space between two giant filter drums. "He doesn't climb the secondary runs unless a rotor seizes completely. He makes you do it because he’s too fat across the hips to get through the crawl-rings."

She set her bucket down and pointed to an iron hatch set into the side of the drum. It was fastened with four heavy wing-nuts, each one secured with a lead seal that had been stamped with the seal of the Crawlspace Guild—a pair of crossed calipers over a rat’s skull.

"Look at the seal," she said.

Milo leaned in. The lead was gray and dull, but where the wire passed through the center, it had been cut clean through with a pair of diagonal nippers, then stuck back together with a tiny dab of yellow grease to keep it from swinging loose.

"Someone’s been inside the drum," Milo said.

"Not today," Vena whispered. "The grease is oxidized. It’s been there at least three days. Maybe since the last time the supply ship came up from the south."

She reached out, took the wing-nut between her thumb and forefinger, and gave it a quarter-turn. It moved smoothly, without the harsh, screeching protest that usually came from bolts exposed to the damp drafts of the lower tiers. The threads were bright with fresh petroleum jelly.

"You said that red line in your book went through forty-nine to the Council floor," she said, looking straight into his eyes. Her face was very pale in the sickly green glow of the instrument lights. "What did it do after that?"

Milo closed his eyes, picturing the thin, ruled line drawn across the zinc sheet. He had spent five years learning the layout of the tubes; he knew the runs like a blind boy knew the bumps on his bunk-frame.

"It didn't stop at forty-nine," he said, the words coming out before he had fully thought them through. "It crossed the intake screen, went through the balancing damper behind the Governor’s gallery, and then it turned down. Straight down through the center core, right into the primary helium envelope."

Vena drew in a sharp breath through her teeth. The air made a whistling sound against her dry lips.

"The helium envelope," she repeated. "The main cell?"

"The one that holds the whole basket up," Milo said. "Number One."

For several seconds, neither of them moved. Above them, through forty feet of steel ribs and copper pipe, the acid rain slammed against the hull with another sudden, shuddering crash that made the iron drum between them ring like a muffled bell. The aerostat gave a long, sickening heave to the starboard as it rode out another thermal wave rising from the boiling sulfur flats fifty kilometers below.

From somewhere down the passage, the sound of heavy boots began to climb the iron ladder, accompanied by the dry, metallic click-click-click of brass fingers tapping against a wrench-shaft.

"Milo!" the voice came roaring through the ductwork, magnified by the iron curves of the pipe until it sounded like it was coming from inside their own skulls. "Milo, you little scoundrel! The pressure on 4-B just dropped four pounds! If you left that damper loose, I'll skin you and use your hide for a pump gasket!"

Vena didn't look at the ladder. She grabbed Milo by the collar of his shirt, hauled him half an inch toward her, and hissed directly into his ear.

"Keep the key in your sock," she said. "And don't you dare drop that notebook down the chute."

She let go of his shirt, snatched up her bucket, and kicked the wing-nut on the filter drum with the heel of her boot, spinning it tight against the collar just as Master Varos’s greasy leather cap appeared at the top of the companionway.