AI The rats had drawn a line around the dead man, and not one of them had crossed it.
Quinn noticed that before she noticed him. The droppings stopped in a clean arc two metres from the body, as if someone had chalked a boundary the vermin agreed to respect. She ducked under the cordon tape and straightened up inside Duncan Street station, closed to the public since 1962 and rotting politely ever since.
The platform lay forty steps down a spiral stair the council had forgotten to seal properly. Green tiles sweated on the walls. A poster for a film nobody alive had seen peeled itself away one corner at a time, and the dust on the floor held the grey, undisturbed patience of decades. Except it had been disturbed . Everywhere.
The dead man lay on his back midway down the platform, arms at his sides, arranged with care. Good coat. Clean shoes. Mid-thirties, at a guess. No wallet, no phone, no keys. A single puncture wound sat over his heart, neat as a tailor's mark, and there was no blood. Not a drop on the coat, not a drop on the tiles. His lips had gone the colour of slate, and his fingertips were black, though the air down here was mild.
A broken ring of salt circled him. Chalk marks curled beneath it in a script Quinn didn't recognise. Six small discs of carved bone lay scattered across the platform like change from a finished transaction, and a seventh sat inside his right fist, which had closed around it tight.
"DI Quinn." DC Mensah picked his way along the cordon path, shoe covers crunching. "Dr Iqbal's done her first pass. You're going to love this."
"Go on."
"Lividity's fixed. He died right there, on his back, and he's been dead two days. Minimum." Mensah flipped his notebook shut . "Except the two lads who found him are urban explorers, and they photographed this platform forty hours ago. Timestamped, geotagged, the works. Empty platform. No body."
Quinn looked at the body. The body declined to comment.
"Camera on the corner," she said.
"Pulled it already. He comes down alone at 02:40, night of the full moon. Nobody else enters. Nobody leaves. Thirty-six hours of empty stairs." Mensah spread his hands . "So. Cult thing. Has to be. Salt, chalk, bone, full moon. Some role-play circle got carried away, stabbed him somewhere else, carried him in dressed like that, staged it, slipped out past the camera blind spot."
"Has to be?"
"It's the shape that fits."
Quinn crouched by the salt line. One section of the ring had been scuffed through, and the scuff marks ran outward from the body, toward the far end of the platform, where an old archway had been bricked up. She walked the length of it, slow, reading the dust the way Morris had once taught her to read a pub floor.
"Come here, Mensah. Tell me what you see."
"Dust. Footprints. Rubbish."
"Count the footprints."
He was quiet for a moment. She watched his mouth move.
"Dozens. Dozens of sets. All over the platform." He frowned. "The camera missed them. That's all. There's a blind spot, there's always a blind spot."
"There's no blind spot. The tunnels both ends are grouted shut and the track bed's flooded to the ceiling. One way in. One way out." Quinn swept her torch beam across the floor. "Look at the dust again. Not the prints. The gaps."
Rectangles. Dozens of pale rectangles pressed into the grime, arranged in rows with aisles between them, each roughly two metres by one. Something heavy had stood in each spot for hours, then gone, leaving no drag marks, no scrapes, nothing carried past the one working camera in Camden.
"Stalls," she said. "Rows of stalls. There was a market down here."
"A market."
"Tally marks on the tiles by the third one. Chalk prices, in no currency I know." She lifted a small twist of waxed paper from beside a rail chair with two gloved fingers. It smelled of myrrh and, under that, ozone, like the air after a strike of lightning. "And this." A coin glinted in the dust at her knee. Silver, worn thin, a profile no monarch had ever worn. A denarius, if her school Latin served. Beside it, a farthing, and a button carved from bone.
Mensah crouched opposite her. "With respect, guv. Occultists collect tat. That's what occultism is. Tat with Latin on."
"Then where did they go?"
"Camera's wrong."
"Cameras don't get embarrassed, Mensah. People do." She stood. Her knees cracked. "Forty hours ago this platform was photographed empty. Thirty-six hours ago a dead man walked down the stairs to attend a market that was already packing itself away. Lividity says he's been gone two days. Do the sum."
"You want me to write that in my notes?"
"I want you to explain how a corpse taps an Oyster card."
He had no answer for that, so he did what he always did, and looked at his shoes. She let him. Three years ago she'd stood in a lock-up in Bermondsey with salt on the floor and Morris at her elbow, making jokes about smudged chalk. They'd logged a bone disc into evidence that night. It had vanished from the store within a week, along with Morris's notes, and two months later Morris had vanished too, into a case file sealed by a unit that didn't appear in any directory. She'd kept one photograph from that floor. The bone disc in it was a twin to the seven on this platform.
"Bagged this from his coat pocket, DI." The scenes-of-crime officer, Pru, held up a clear sleeve. Inside sat a small brass compass, its casing furred with verdigris, its face etched with sigils that matched the chalk work under the salt. "Odd thing. Needle's jammed."
Quinn took the bag. Through the plastic, the needle sat steady, pointing down the platform at the bricked arch. She turned the compass a half circle in her hand. The needle did not swing back to north. It held on the arch, patient as a dog at a door.
"Broken," Mensah said, with relief.
"Compasses don't break in one direction." She walked to the arch . The bricks were new. The mortar between them was newer still, pale and damp, weeping down the courses in thin tears, and the rats' boundary curved wide around this spot too, as if the whole platform's vermin had voted on it. She set her palm flat against the brick. Cold. Colder than the room had any right to make it.
"Fresh work," Mensah said behind her. "Kids. Squatters."
"Bricked from this side, recently, in a sealed station nobody's entered in weeks." She stepped back . "He came here for the market. He bought something or he failed to. And when it was done, they left him on the tiles like a receipt, and bricked up whatever they'd used as a door."
"Guv." Mensah lowered his voice. "Hear yourself. This is a murder inquiry. Morris, he," and he stopped, because she'd turned around.
"Finish it."
"You see this case everywhere. That's all anyone says."
"Anyone can stop saying it when the evidence stops rhyming."
She went back to the body and knelt. Up close, the coat told its own story. The lining at the left seam had been picked open and restitched with thread that didn't match, clumsy, hurried. She worked it open with a gloved nail and drew out a slim rectangle of card.
E. Kowalski. Research Assistant. Restricted Archives, British Museum. A telephone number in print beneath. On the back, in pencil, in a hand that wrote quickly and thought faster: Full moon. Fee in bone.
"Find me everything on that name before sunrise," she said, and held the card up to Mensah, "and get the museum on the, "
"DI Quinn." Pru's voice had changed. Gone thin. She stood over the body with her camera hanging at her side. "The fist. His right fist. It's open."
It was. The dead man's fingers lay loose against the tiles, palm upward, empty. Quinn had photographed the bone token in that hand herself not twenty minutes ago, and the photograph still showed it on her screen, snug in the grey curl of his fingers. Nobody had touched the body. Nobody had crossed the cordon path.
The evidence bag warmed against her palm. Inside it, the needle had moved. It no longer pointed at the bricked arch. It had swung a quarter turn, past the salt, past the body, and now held steady on the tunnel mouth at the platform's end, where the dark sat thick as tar.
Quinn lifted her torch. The beam went in six metres and came back empty. Grouted arch. Floodwater. Nothing.
Then, from somewhere inside that nothing, came the bright small ring of a brass bell, the kind a shop door makes, followed by the low murmur of a crowd at trade, cut off all at once, as if a door had closed.
"Tell me you heard that," Pru said.
Quinn didn't answer. The needle held on the dark, steady as a pointing finger.