AI Quinn hit the slick cobbles sideways and kept running.
Her shoulder clipped a parked scooter, sent it rattling. Ahead, the suspect glanced back once, pale face a flash under the streetlamp before he sliced between two honking taxis and vanished behind a spray of filthy water.
She tasted exhaust and wet brick. Her lungs burned but her stride stayed even, arms pumping in drilled rhythm. Eighteen years on the job, ten before that in uniform, her body knew pursuit better than sleep.
The radio crackled at her hip.
"Quinn, update."
"Visual on target, Camden High Street, heading north." Her breath came sharp between words. "Male, mid twenties, hoodie, black rucksack. Suspected link to Blackfriars crime scene."
"Units diverting."
"Negative. Do not spook him."
"That is not your call, Detective."
"It is tonight."
She killed the volume with a thumb and veered into the road. Tyres screamed. Horns flared. A bus loomed but she cut in front of it, coat snapping around her knees, mind cold and fixed.
The suspect darted past a kebab shop, slipped on the wet pavement, slammed a hand to the glass to steady himself, then bolted again. A woman carrying a takeaway shouted abuse as Quinn barreled past.
He turned left, into a narrow gap between a vape shop and a boarded up newsagent. No CCTV there. Dead ground. Her jaw set.
Of course he knows the blind spots.
She forced herself not to think of another chase, another partner, a stairwell that ate radio signal and spat back silence . DS Morris lying crumpled in the dark. The coroner had written "blunt force trauma" with tidy ink. The photographs had shown something else lurking at the edge of the frame, a shadow that did not belong.
Quinn hit the alley mouth, shoes slapping through oily puddles. The stink here changed, hot rubbish and stale beer, the greasy hum of extractor fans. The suspect ran low and nimble, trainers splashing, rucksack thudding against his spine.
"Stop, police."
He did not even flinch.
He cut right, under a half rolled shutter tagged with looping graffiti. She saw his hand flash, something bone white between his fingers, and then he vanished into the dark.
Quinn skidded to a halt at the shutter. A gap at the bottom, just wide enough. Beyond lay a sloping concrete ramp and a draft of air that came from somewhere deep, smelling of old stone and damp metal.
Her watch ticked against her pulse . Worn leather against damp skin.
She dropped to one knee, flattened herself and slid under. Rust scraped her back, caught her coat. For a second she felt pinned, trapped, the metal kissed the nape of her neck.
Not here. Not like Morris.
She exhaled hard, pushed through, and tumbled onto the ramp.
The sound changed at once. The muffled roar of the street thinned, replaced by a hollow hum, a murmur from below like a crowd behind thick glass.
She pushed up and drew her sidearm. The suspect's footsteps echoed faintly down the ramp.
She moved, low and steady, eyes adjusting. Emergency strip lights glowed along the ceiling, some dead, some buzzing. The walls showed the old cream tiles of a disused Tube entrance, cracked and stained, adverts from another decade peeling in tatters.
Someone had prised the TfL roundel from the wall. In its place hung a black disc painted with a single white line, jagged, like a crack through stone.
Her boots hit the first of the stairs. Chalk symbols looped across the steps, half scrubbed, half fresh. Circles intersecting triangles, letters that belonged to no alphabet she knew. She had seen similar marks in Morris' final case file, photographed on a warehouse floor in Rotherhithe before someone higher up had stamped the folder classified and pulled it from her hands.
The memory tried to slow her. She forced herself to keep moving.
Below, the suspect's steps quickened .
"I can hear you." Her voice rang down the shaft. "You will not outrun me underground."
A man's voice floated back, distorted by the curve of the stairwell.
"Wrong tracks, copper."
It carried a laugh, wrong for the words, too calm. She felt the hairs rise on her arms.
The staircase turned twice, then spat her into a wide landing with ticket barriers frozen in mid service, gates locked open and rusted that way . Beyond, twin escalators, their metal teeth still.
The suspect pelted toward the platform level. One hand went to his pocket.
"Stop." Her shout cracked against the tiles. "Hands where I can see them."
He sprinted quicker.
He reached the top of the escalator, pivoted hard, vaulted the dead handrail, and dropped out of sight.
Quinn reached the edge and looked down.
Not a platform. Not anymore.
Where the escalator once descended to trains, someone had broken through. The bottom third of the stairway ended in a jagged cut of concrete that opened into a larger void, a tunnel whose brickwork looked older than the station itself. Lights glowed down there, warm and gold, flickering like candle flames. The murmur she had heard thickened, turned into many voices, some human, some not.
Her mouth went dry.
She took the easier path, ran down the escalator the proper way, metal steps clanging.
Halfway down she saw him again, at the broken edge, facing a man in a long dark coat. The coat hung straight, too clean for this ruin. The man held out his hand.
"Token."
The suspect dug into his pocket, pulled out the white thing she had glimpsed. Not a card. A sliver of bone, worn smooth by many fingers, drilled clean through at the centre. It looked like a knucklebone from a child's game, polished until it gleamed.
The man in the coat took it between thumb and forefinger. His nails looked wrong, too thick, cut square. He closed his hand around the bone, then opened it again.
The token flared dull red, glow dull as ember. The man watched Quinn approach, eyes hooded, then turned and pressed the bone against a patch of brick beside him.
The wall rippled.
Bricks that had stood solid for a century sighed and folded in, mortar running like mud. A gap appeared, an arch just wide enough for a person.
Warm air breathed out, thick with spices, sweat, and something metallic that brushed the back of her tongue.
The suspect slid through the arch without looking back.
The man in the coat stepped to block the opening as it started to congeal closed again.
Quinn raised her gun.
"Step aside."
He smiled, small and sharp.
"No jurisdiction past this point, Detective."
Her finger tightened.
"You know my name."
"Your reputation travels." He tapped his chest, right above where a warrant card would hang on a copper. "This is not your kind of market."
She reached the bottom of the escalator and came to a halt three metres from him. Up close, his eyes had a milky sheen, like there was a second film over the iris.
"Market for what."
"Things people want. Things they should not want."
"The man who just went through, he is wanted for questioning in a murder investigation. Move."
"He has paid his way. You have not."
He angled his body, not quite braced to fight, not quite relaxed . He never took his hand off the slowly hardening bricks.
Behind him, in that brief gap, she saw a fragment of the world on the other side: a stall draped in faded velvet , strings of coloured glass, a figure with too many rings stacking clear jars filled with something that glowed faintly.
Then the bricks pushed back into place, and the crack sealed with a wet stone sound.
The bone token in the man's hand cooled to ivory again.
He tucked it into his pocket.
Her muscles went tight.
"You are going to open that again."
"You are going to go back up those stairs."
"You think so."
"I know so." He nodded at her gun. "You fire that here, it echoes for days. People ask why you brought the surface rules down. They take it badly."
Her radio buzzed against her hip again, faint, as if the signal had to force its way through something thick.
"Quinn, status. Respond."
She ignored it.
Her world had shrunk to the man, the sealed wall, the dryness in her throat.
There had been odd things before, odd enough to wake her at night. Bodies with no clear cause of death, CCTV that skipped at just the wrong moment, witnesses who swore shadows moved against the light. She had filed reports and watched them disappear into locked cabinets.
That was all noise.
The door in front of her felt like signal .
"What is that place."
"Beneath."
"Beneath what."
"Everything you pretend does not exist."
His smile widened, only a fraction, but enough.
"You cannot follow."
"You prepared to bet on that."
She stepped closer. The floor felt wrong under her soles, too smooth for cracked concrete, as if something had worn a groove in it, back and forth, many times.
He watched her hands. She watched his feet.
He moved first, tried to pivot and bring his shoulder into her, body checking her off balance.
She caught his wrist, turned with the motion and used his weight . Judo lived in her bones. He went down hard, shoulder cracking against a dead escalator's metal lip.
Something small and pale flew from his pocket and skittered across the tiles, bone flashing in the light.
He grunted, came up with a knife in his off hand, arm sweeping low toward her thigh.
She stamped his wrist to the floor. Steel pinged loose. His breath knocked out of him in a harsh curse.
"Stay down."
He spat blood at her boot.
"You drag that blade upstairs, I book you for possession and see how long you last in remand."
"You drag that gun downstairs, and you do not last ten minutes."
His eyes glittered, no longer hooded.
Quinn kept her boot on his arm and scanned for the bone. It lay near the wall, still, a dull little thing for all the weight it seemed to carry.
She shifted, never fully taking pressure off him, and picked it up.
Warm. Too warm for something that had sat on cold stone. The hole at its centre seemed deeper than it should, shadow pooling inside .
He hissed.
"That token does not belong to you."
"Now it does."
"You have no idea what waits on the other side."
Her watch ticked high and fast.
Her radio crackled again, more distant this time, as if her own world stepped back from her.
She saw Morris' hand in her head, fingers reaching toward her out of the darkness at the bottom of that stairwell, skin slick, wrist bent wrong. Saw the black smudge on the wall opposite, like something had pressed itself flat and left a stain without ever having a body.
If she walked away now, this door would close in more ways than one. The suspect gone. The market sealed. The questions in her case files stayed questions.
Her voice came out softer.
"What is inside."
The man lay half pinned, chest heaving.
"Debts."
He bared his teeth.
"And things that know your name before you speak it."
She lifted her boot from his wrist and stepped back.
He stared, confusion chasing defiance across his face.
"Quinn, do not be stupid."
"Oh, I am tired of clever."
She raised the bone and pressed it against the same patch of brick he had touched.
For a moment, nothing happened. Just brick, cold and harmless.
Then the token burned.
Heat drove into her palm. She clenched her jaw , refused to drop it. The bone's glow woke, ember to coal to a soft blood red. The wall unstuck from itself and peeled back with the sound of a slow inhalation.
Warmth and scent rolled over her.
The space beyond unfolded.
The tunnel opened into a cavern carved from the bones of the old station and something older, arches ribbed like a beast's cage. Fairy lights tangled with exposed wiring. Stalls grew from the brick, patched together from shipping crates, carved wood, antique doors. One glimmered with knives that drank rather than reflected light. Another spilled glass bottles stoppered with wax, each containing smoke that pressed against its prison.
Voices rolled and crashed. Human, almost human, not human at all.
A woman with hair like ink and eyes reflective as a cat's argued in French over the price of a jar filled with teeth. A hunched figure with mottled grey skin and a Saint George's flag stitched to his bomber jacket shook dice into a customer's palm that crawled of their own accord. Somewhere, something that sounded like a child and not like a child laughed and laughed.
Quinn swallowed.
The man behind her scrambled up on one elbow.
"Detective. Last chance. Back out."
She slid her gun into its holster, not from trust but because she had seen enough crowds turn feral at the sight of a firearm. She slipped the bone token into her coat pocket, feeling its heat soak through the lining.
Her throat felt raw.
"That suspect," she said, never taking her eyes off the riot of the market, "where does he run in there."
"He will know the way. You will not."
"Then I learn fast."
She stepped through the arch.
The air closed around her different, thick and humming. The ground shifted under her feet, no longer plain tile but a patchwork of worn rugs, beaten earth, and something like old train ballast .
Conversation faltered near her, like a record skipping. Heads turned. Faces followed, some with too many eyes, some with features that did not settle.
She heard the man in the coat get to his feet behind her. He did not follow. That told her enough.
A woman at a nearby stall watched Quinn with open interest. She wore a man's suit that hung on her sharp frame like it missed a body inside it, throat bare, no tie. On the table before her, little bottles of dark liquid shivered in their trays as if they had nerves.
"Lost, love."
Her accent carried old East End, vowels long and lazy.
"Looking for someone," Quinn said.
"Down here every bastard is looking for someone. Or something to fix the ones they have lost."
The words landed with unpleasant accuracy.
Quinn scanned the crowd, searching for black hoodie, rucksack, guilty shoulders. The suspect threaded his way through a knot of figures near the far curve of the cavern, head ducked, making for a darker passage where the light thinned.
Her pulse kicked.
"There," she breathed.
The woman followed her gaze.
"That one," she said, "has paid safe passage. You have not."
"Send me the invoice."
Quinn moved.
The crowd resisted. Not overtly. A step here, a stall jutting that had not been there a heartbeat before, a group of cloaked figures drifting together in front of her as if drawn by sudden conversation. The air tasted off, sweet then bitter, like she had bitten into overripe fruit.
She dodged a hanging cage where something small and winged beat itself against the bars hard enough to rattle the chain. A hand with scales instead of knuckles brushed her sleeve and withdrew. Murmurs rustled in her wake.
"Surface law," someone said.
"Wrong boots," someone else snickered.
Her eyes never left the line of the suspect's back. He reached the edge of the main chamber and slid into the side passage, lit by fewer bulbs, their glow jaundiced and sickly.
She pushed harder.
A tall man in a velvet coat stepped into her path and raised a silver flask.
"To new blood," he said.
She shouldered past him.
"Find another toast."
He caught her arm with cold fingers.
"Careful where you spill your authority, Detective. Some of us lap it up."
She twisted free. His grip left her skin tingling, as if he had touched a nerve instead of flesh.
She reached the mouth of the passage and paused for half a heartbeat.
The tunnel beyond fell away into darkness broken by irregular lamps hammered into the walls. Symbols cut into the brick pulsed faintly, out of sync with any sane rhythm. The hum in the air thickened, no longer social, now structural, like the market itself had a heartbeat buried deep.
Behind her, the crowd's noise rose again, louder, less curious and more interested, like spectators sensing a fight.
Her radio on her hip gave one last stuttering burst and died, screen blinking to black.
She stood between two worlds, both watching.
Her palm brushed the bone token in her pocket. Still warm. That heat seemed to seep up her arm and settle behind her breastbone, a false heart.
She thought of the neat tick of her watch , of Morris' name etched on a memorial wall, of case files that ended not with closure but with transferred, reassigned, discontinued .
Ahead, in the gloom , a shadow moved, light catching the edge of a black rucksack as the suspect broke into a run again, deeper into the unknown.
Quinn stepped after him.
The ground dropped, a shallow ramp that felt steeper in the half light. The walls closed in, damp beading on the brick. A metallic tang grew stronger, cutting through the spice and sweat from the main hall. Under it, a subtler smell, old hospitals and long cleaned blood.
The suspect glanced back, eyes wide now that the crowd had thinned and he could see who stalked him.
"You do not want to be here," he called.
"I am already here."
"You think murder is what this is about."
He laughed, a short ugly sound.
"This is about debt."
He swung his rucksack off his shoulder mid stride, dragged at the zip.
Quinn reached for her gun.
The nearest lamp flickered and flared out, then the next, plunging the passage into stuttering shadow. The symbols in the walls brightened, their glow crawling like sick light under skin.
He tore something from the bag. A compact bundle wrapped in brown paper, string cutting deep into the corners.
He hurled it to the floor between them.
The paper split.
Something inside hit the ground wet and heavy.
The smell exploded first, sharp copper and rot, like every slaughterhouse she had ever walked through jammed into one breath. A pale hand rolled free, fingers crushed into a fist.
Quinn's vision pinpricked, not from shock, but from the way the bricks around the package pulsed, lines of faint light racing out from the meat like veins seeking a heart.
The ground shivered under her boots.
Behind her, at the tunnel mouth, the market noise shrieked and cut as if someone had sliced a record.
Ahead, the suspect stepped back, lips moving silently as if reciting .
The walls bulged inward.
From the meat on the floor, from the pale hand, from the web of light in the brick, something began to pull itself upright.