Patch had been walking in circles for three days, and his stuffing smelled like wet coal. He knew because he had passed the same broken lamppost four times. He was a teddy bear the size of a loaf of bread, with a black eye patch stitched over one button eye and a small sword strapped across his back. Somewhere below this maze of pipes and dripping brick, the girl who had loved him into life was lost. He meant to find her before the smog ate her lungs. The tunnels changed. He was sure of it now. A passage he had marked with a scratch was gone the next hour, replaced by a wall of sweating iron. Without a map, he would rot before he found her. He needed someone who understood how the underbelly moved. He climbed a ladder toward a crooked light and found a toy shop wedged between two leaning chimneys. The sign above the door still promised delight in faded paint. Patch pushed inside. Gears clicked. A rocking horse with no head rocked by itself in the corner. A rail-thin woman knelt on the floor, prying the eyes out of a porcelain doll with a screwdriver. Cracked goggles pushed her ink-black hair off her forehead. Her coat was covered in stitched-on paper — blueprints, Patch realized, each one crossed out. She did not look up. "Door's shut for a reason," she said. "Toys walk out, they don't walk in." Patch drew his sword. It was the length of a nail file. He set it on her workbench, hilt toward her. "I need a map of the tunnels. I can pay." She finally looked. Her eyes moved from the sword to the eye patch to the coal dust matted in his fur. She snorted. "No map exists. The pipes shift when the furnaces breathe." "Then I need something that shifts with them." She went still. Then she stood, crossed to a shelf, and lifted down a brass compass the size of her palm. Its face was open. Tiny gears turned inside it, chasing each other in slow circles. "Prototype," she said. "Reads pressure, not north. Follows the live vents." She held it out but did not let go. "Why should I give it to you?" "A witch is down there….She’s being held prisoner.” His voice was cloth and gravel. "She’s my friend. I have to save her!” The woman's mouth twitched. She let the compass drop into his paw. "It's not finished. The needle sticks when the air goes bad. When it sticks, you run." Patch closed his paw around the brass. It was warm, and heavier than he was built to carry. "One more thing," she said as he turned for the door. "The vents lead down to the sump. Whatever's taken your witch — it lives there too." Patch stepped back into the smog. The needle inside the compass began to turn.

The compass pulled Patch downward for hours. The needle jerked left at a rust-choked junction, then steadied on a low tunnel where the smog thinned to a pale haze. He followed it until the brick gave way to worked stone. A round door sat in the wall, carved with vines and small moons. Warm light leaked under it. Patch had expected a pit. He had found a nursery. He put his ear to the wood. Someone was humming. The tune broke off and started again, wrong each time. He drew his sword and pushed the door open a finger's width. Inside, the room was too clean. A rug. A low cot. A kettle on a small stove. On the rug sat the witch who had cried him awake. She was grown tall now, taller than he remembered, in a starred robe and nothing else below it but a thick white diaper. A pink pacifier bobbed in her mouth. She was stacking wooden blocks and knocking them down. Patch's stuffing went tight. He stepped inside. "Bella," he whispered. She looked up. The pacifier fell into her lap. Her eyes filled, cleared, filled again, like something was fighting for the front of her head. "Bear," she said. Then, sharper, "Patch. You shouldn't— sorry, blocks are very— okay. Focus." She pressed her palms to her temples. "Someone hexed me. At the school. I came down here to break it alone so nobody would see me like— well. Like this." She gestured at the diaper. "Yeah. It's as bad as it looks." "Who's keeping you?" "The smog keeps me. It likes soft things." She giggled, clapped a hand over her mouth, and glared at it. "Sorry. Not funny. It thickens if I try the door. I've tried the door a lot." Patch climbed onto the cot and cut the ribbon someone had tied around her wrist. The knot was warm. It hissed when it parted. Bella gasped and sat up straighter, like a string had been cut inside her too. "Compass," he said, holding it out. "It follows live vents. We go out the way I came." She took his paw. Her hand was bigger than his whole body. They went to the door. The door was gone. Only stone stood where it had been. Behind them, the kettle began to whistle on its own. The pale haze at the ceiling darkened and lowered. The compass needle swung once, twice, and stuck. Bella looked at the needle. Then at Patch. The pacifier drifted back toward her mouth and she slapped it away. "Okay," she said. "It knows you're here now. That's worse." Patch tightened his grip on the sword. The smog was already sliding under the vanished door, feeling for them along the floor.

The smog pressed under the stone where the door used to be. Patch shoved Bella toward the wooden toy box in the corner. She went without arguing, which scared him more than the smog did. She folded her tall body down behind the box and pulled her starred robe over her knees. The pacifier dangled from its clip against her chest. Her hand shook. Patch climbed into the box itself, buried himself under painted trains and blocks, and left one eye clear between two wooden wheels. Something tapped the far wall. Once. Twice. Then the stone opened like it had never been closed. A porcelain face ducked through the doorway. Eight brass legs followed, folding neat to fit, then spreading wide across the rug. Patch had heard the toy shop woman describe things that came down from the upper city to collect stray children. He had not believed her until now. The nanny's mask had three fine cracks near the left eye. Her skirts were black. Her hands were gloved and small. "Child," the nanny said. Her voice was flat. "You are damp. Stand up." Bella stood. Her face went slack around the pacifier, which had somehow found her mouth again. She started toward the nanny like a wound toy. Patch pushed a train off his chest. The nanny's head turned at the sound. One brass leg lifted and pointed at the box. "Mice," she said. "I will deal with mice after." She knelt on four legs and reached for the tapes at Bella's hip. Bella's eyes cleared for one blink and found Patch through the slats. She gave the smallest nod. Patch came out of the box sword first. He landed on the nanny's back between two leg joints and drove the blade down through the brass collar where her neck met the body. Something inside her ticked, then screamed like a kettle. She reared. Her legs skidded on the rug. Patch held on with one paw and sawed. A gear popped out and rolled under the cot. The porcelain mask cracked from the left eye to the chin. She fell sideways and did not get up. Her legs kept moving, slower, slower, then stopped. Bella spat the pacifier onto the rug and stepped on it. "She came through the wall," Bella said. "Patch. She came through the wall." Patch pulled the compass from his cloak. The needle was still stuck. He pointed at the hole the nanny had opened. It was already narrowing, the stone knitting shut. "Go," he said. Bella grabbed him under one arm like a doll and ran. The gap closed on her trailing hem and tore it. Then they were in a new tunnel, dark, warm, and the smog was behind them. Something further down the tunnel tapped the wall. Once. Twice. Waiting.

The tapping stopped when Patch stepped into the tunnel proper. Bella set him down. The warm dark smelled of chalk and old milk. Small doors lined both walls, painted with rabbits and moons, and each door hung ajar on a different room. A crib here. A rocking horse there. The passage bent, split, bent again. It was a nursery grown sideways into the rock, and it had no end Patch could see. He pulled the brass compass from his cloak. The needle spun, caught, spun again. Every vent in this place breathed the same soft air. The compass had nothing to bite on. "Bella. Which way is out." She stood in the middle of the hall with her thumb near her mouth. She pulled it down. "I know this place. I think. No. I knew it. It's like a word I had this morning." She looked at him. "I'm sorry. My head is full of soft stuff." The hex. He had cut one ribbon off her wrist in the chamber. Others were still on her, invisible, holding her small. He drew the sword. "Give me your hand." "Patch." "Not to cut you. Hold still." She held out her wrist. He laid the flat of the blade across her palm and pressed his one good eye shut. He thought of the witch who had cried him awake. He thought of Bella at fifteen, sneaking him sugar in the kitchen. He pushed that thought down the steel. Bella gasped. A thread lifted off her skin, thin as a hair, and curled around the blade. Another. Another. Not all of them. Just enough. She swayed and caught the wall. "Oh," she said. "Oh, that's a lot of me." She wiped her eyes with her sleeve. Still wearing a diaper. “Let's name that and move on. Left." "Left?" "Third door past the horse. The one with the moon. There's a stair behind the wardrobe. My aunt used to hide sherry in it." She almost smiled. "The stair, not the sherry." Patch sheathed the sword. The threads on the blade snapped and drifted down like burnt hair. The compass needle steadied and pointed where she had. Patch ran and Bella waddled behind still in her diaper. Past the rocking horse. Past two doors. The third had a moon on it. Inside, a wardrobe stood open, clothes shoved aside. Behind the clothes, stone steps went up. Bella stopped at the first step. Her hand shook on the frame. "Something knows," she said. "Patch. I felt them notice when the threads came off. The rest of them. My school." Above the stair, far up, a bell rang once. Clean. Cold. A calling bell. Patch drew the sword again. "Up," he said. She went up. He followed. Behind them, every small door in the nursery hall clicked shut at the same time.

The stair let out into a narrow hall of raw brick. A single gas lamp guttered on the wall. Behind Patch, the door they had come through sealed itself into the stone. Bella pressed her palm to where the seam had been and pulled it back covered in soot. "Gone," she said. "That's fine. That's normal. I hate it." Patch kept his sword out. The hall bent sharp to the right. From around the corner came a wet copper hiss, like a kettle sighing through its teeth. "Behind me," Patch said. He stepped around the bend. The thing filled the hall wall to wall. It was a copper pot on stubby legs, tall as Bella, riveted and dented, with a wide rim and a painted face pushed to one side. Little vents on its shoulders puffed white steam. Its eyes were huge and green and glad to see them. It giggled. The sound came out of a spout somewhere inside it. "Oh no," Bella said, very small. "Oh, no, no. I know what that is. That's for accidents. That's what they send when a girl has an accident." The copper thing waddled forward. Steam curled from its rim. It opened its arms. Patch swung. The sword rang off the copper belly and jumped in his paw. Not a scratch. He struck again, low, at the ankle joint. The blade bit and stuck. The thing giggled again and lifted its foot, and Patch went up with it, hanging off his own sword. "Bella. Run." Bella didn't run. Bella backed into the wall with her hands over her face, and Patch heard the crinkle before he understood it. Then the smell. Then Bella making a noise that wasn't a word, high in her throat. "I did it again," she said into her hands. "I did it. I'm sorry. I'm sorry, I couldn't, it just — it just went." The copper monster stopped. Its green eyes went to Bella. Its face did something like a smile. It set its foot down gently, with Patch still dangling, and reached for her with both arms open, cooing through its vents. It wanted her wet. That was the whole point of it. Patch yanked the sword free and dropped. He rolled between the monster's legs. Under the belly he saw what he needed: a brass drain plug the size of a saucer, screwed into the bottom. He hooked the sword's guard into the slot and threw his whole weight sideways. The plug spun. Popped. A gout of scalding water crashed down over the stone. The monster shrieked through every vent at once, tipped, and clanged onto its side. Steam boiled up the hall. Patch grabbed Bella's hand and pulled her past it, over the puddle, into the dark ahead. She was crying. Still walking. Still wet. "Keep moving," Patch said. "We'll fix the rest when we're out." Behind them, in the steam, something else began to giggle back.

The giggling behind them faded into the steam. Patch pulled Bella another ten steps before her knees folded. She slid down the brick wall and sat in the soot with her legs out straight. The pacifier had fallen from its clip and dangled at her chest. Her hands shook. Her breath came in small, wet hitches. "I can't," she said. "I can't, I can't. My legs went stupid." She pressed the heel of her hand into her eye. "Sorry. That's a bad word for legs. They went numb. Same thing." Patch crouched in front of her. The hall stretched on into the dark. He could hear air moving somewhere above — a real vent, pulling up. The surface was up. They had to keep going up. He pulled the brass compass from under his cloak. The needle wobbled, then leaned steady toward the draft ahead. Good air. Not far. "Bella. Look at the needle." She didn't look. She was staring at the wet patch on her diaper and crying without sound. "They send another one," she whispered. "If I sit here. They always send another one." Patch set the sword down. He set the compass down. He took her cold hands in his paws. "Listen. The witch who made me. You know who I mean." Bella's eyes moved to his face. One nod. "She cried for a week straight," Patch said. "Snot on my ear. Tears in my stitching. She said sorry about a hundred times for getting me wet. I didn't care then. I don't care now." He squeezed her fingers. "Wet is not the problem. Sitting is the problem. Get up." She made a noise that was half laugh, half hiccup. "That's a mean pep talk." "Good. Stand." He clipped the pacifier back to her robe. He put it in her mouth himself. Her jaw locked on it. Her breathing slowed. Three breaths. Four. The shaking in her hands dropped a notch. Patch stood and held out a paw. "One step. Then another one. That's the whole plan." Bella took the paw. She got her feet under her. She swayed, caught the wall, and stayed up. "One step," she said around the pacifier. She took it. Then another. Patch walked backward in front of her, compass in one paw, her hand in the other, sword tucked under his arm. The needle held its line. The draft got stronger. Somewhere far above, through brick and pipe, he heard the flat clang of a bell. Bella heard it too. She stopped. "That's my school," she said. The pacifier fell out. She didn't catch it. "That's them. They know where I am now." Patch looked up at the ceiling. The draft on his fur turned colder. The compass needle twitched once, hard, and stuck.

The bell rang again above them. Bella flinched. Patch tapped the compass hard against his paw. The needle stayed stuck, quivering like it wanted to point everywhere at once. "It's not reading air anymore," Patch said. "It's reading them." "My school." Bella wiped her nose on her sleeve. "They'll send someone through the walls. Faster than the nanny thing. Sorry. That's not helpful. I'm just saying." Patch looked back the way they'd come. Steam hissed from a low grate. He thought of the toy shop far above — the woman with the patched coat who gave him this compass, who said the pipes shift with the furnaces. If the compass couldn't read air, they had to read air themselves. He knelt and put his paw flat on the brick floor. Warm. He moved along the wall, paw sliding. Cold patch. Colder. A seam in the mortar leaked a thin draft against his fur. "Here. Fresh air behind this one." Bella crouched beside him. She pressed her palm to the brick and nodded. "That's up. That goes up." Patch drew his sword. He worked the tip into the mortar seam and levered. Grit fell. He worked the next brick. His shoulders burned. Bella pulled loose bricks free with both hands and stacked them quietly against the wall. She was crying again but her hands stayed steady. "Almost," she whispered around nothing — the pacifier was gone, lost back in the hall. "Almost, almost." A brick gave. Cold air rushed through. Patch smelled coal smoke and, under it, a hint of the upper city — bread, wet stone, a horse somewhere. Real air. He pulled two more bricks. The gap was bear-sized. Witch-sized if she squeezed. "You first," he said. "Patch." She grabbed his cloak. "The bell. If they come down and I'm gone, they follow the thread. There's still a thread. I can feel it in my ankle now. They moved it." He stared at her. "Another one." "They always have another one." He pushed her toward the gap. "Then we cut it up top where I can see. Go." She went. Her robe caught, tore, went through. Patch grabbed the compass and the sword and climbed after her. They came out in a low brick shaft. A slit of grey daylight showed at the top. A rusted ladder ran up the wall. Not the toy shop. Not the woman with the patched coat. But up. Sky-up. Bella sat on the shaft floor and lifted the hem of her robe. A red thread was knotted around her ankle, warm and pulsing like a small heart. Above them, in the daylight, a shadow moved across the slit and stopped. Someone was already waiting at the top of the ladder. Patch tightened his grip on the sword. "Stay behind me. We climb anyway."