The thread had crossed his wrist by five in the morning.
It was no longer thin as horsehair. In the watery tallow-light of the dormitory washroom, the vein looked like a length of soaked hemp sewn beneath his flesh, swollen and purple-black against the pale tendon of his forearm. The skin above it did not throb. It felt hollow, the way a pine branch feels hollow right before the winter ice snaps it clean off the trunk.
Corin ran the cold tap. He shoved his forearm under the brass spout until the iron-colored water ran over his knuckles and splashed into the basin. The water was near freezing, piped straight from the lake bed, but his right hand registered only pressure. No cold. No sting. Just the dead weight of meat waiting for a spade.
He dried his arm on his sleeve. His grandfather had taught him the rule of necromantic rot on his eleventh birthday, after an apprentice from St. Mungo’s brought in an eighteenth-century hand of glory with the wrist-ligatures still weeping grave-fat: *If it drinks three inches of your blood, it owns the bone. If it takes the elbow, you give the surgeon five Galleons and pray his saw is clean.*
Corin had seven inches left before the bend of his arm.
He pulled his wool cuffs down, buttoned them with his left fingers, and slid his penknife up his sleeve.
The dungeon corridors at dawn smelled of damp moss and coal gas. The castle was dead quiet, save for the low, rhythmic churning of the drainage grates beneath the flags. Filch would be on the fourth floor, dumping sawdust where a second-year had vomited after drinking stolen butterbeer; Mrs. Norris rarely ventured into the Slytherin vaults because the salt in the mortar irritated her paw pads.
Corin turned down the corridor leading to the Potions classrooms.
He did not head for the student supply press. That cabinet held nothing but powdered beetle eyes, dried nettles, and third-grade lacewing flies gray with age. To halt an Elder-branch rot, you needed beaten silver-leaf suspended in wintergreen and oil of vitriol. It was an alchemical cautery—not a cure, but a bridle. It bound the necrosis to the metal, turning the poison back on itself before it could poison the heart.
Only Slughorn kept silver-leaf. He used it as a stabilizing agent for his private batches of draught of peace, which he bottled in crystal for the Ministry undersecretaries who sent him candied pineapples at Christmas.
Slughorn’s office door was dark bog-oak, banded in pig iron.
Corin did not touch the ring handle. He crouched by the lower hinge, his left hand fishing two narrow steel needles from the hem of his trouser cuff. They were seam-probes, ground flat at the tips. He slid the first into the keyway above the escutcheon, feeling for the bronze tumbler.
*Click.*
The pin gave. It was a standard Goblin-pattern lock, forty years old, identical to the ones his uncle installed on the pawn drawers behind the counter. Slughorn had wealth, but he had the laziness of a man who believed the castle’s wards were his personal guard dogs.
Corin eased the second needle in, levered the bottom catch, and leaned his shoulder against the oak.
The latch lifted with a muffled scrape.
The office was stiflingly warm. A coal fire burned low in the round grate, throwing dull orange embers across the Persian carpet. The air carried the heavy, sickening scent of clove water, Turkish tobacco, and the sugary dregs of mead left in unwashed goblets. Framed photographs covered the walls, their occupants frozen in polite, endlessly repeated smiles, raising crystal flutes to an unseen ceiling.
Corin stepped inside and closed the door until the bolt sat against the strike, unthrown.
He moved behind the leather sofa toward the curtained archway at the back. The velvet drape smelled of moth-repellent and damp fur. Beyond it lay Slughorn’s private store annex—a narrow, stone-ribbed closet lined with cedar shelving and jars sealed with red paraffin.
Corin did not light his wand. The orange glow from the hearth reached through the curtain in a thin, dusty stripe.
He scanned the second shelf.
*Essence of Murtlap.* *Ground horn of Erumpent.* *Powdered Bicorn, Grade A.*
On the third shelf, tucked behind a stoneware jar of preserved plimpy eyes, sat a squat glass pot with an octagonal lead lid.
Corin pulled it down with his left hand. The lead was heavy, stamped with the mark of an apothecary in the Shambles: three silver hammers over a crucible. Inside, floating in thick, pale green oil, were dozens of gossamer sheets of beaten leaf, shivering like fish scales in the dark.
He set the jar on the workbench. He opened his penknife with his teeth.
The curved pruning blade caught the embers from the hearth. It was sharp enough to split a hair lengthwise. Corin rolled his right sleeve up to the elbow.
The purple-black cord under his skin had advanced another half-inch while he worked the lock. It was rigid now. A fine, dark frost had begun to crust around the hair follicles near his pulse, the skin turning the color of skimmed milk.
To take the leaf, the rot had to smell fresh iron.
Corin pressed the tip of the blade to the skin directly above the vein, an inch below his wrist-bone.
He didn't hesitate. Hesitation in shop work meant jagged cuts, and jagged cuts took gangrene. He drew the steel across the black line, scoring the flesh three inches down toward the base of his numb thumb.
The cut did not bleed red.
A thick, dark sludge welled into the groove, smelling sharply of copper filings and pond scum. It was cold as slush. He reached into the glass jar with his penknife, hooked three shivering squares of the silver-leaf from the oil, and slapped them flat against the open wound.
The reaction was instantaneous.
The silver didn't dissolve. It screamed. A high, thin whistling sound rose from his arm as the metal bit into the tainted blood, sizzling like bacon fat dropped on a red stove.
Corin jammed the knuckle of his left index finger between his teeth and bit down until the copper taste of his own mouth filled his throat. His knees hit the stone floor. His vision went white, then mottled red, the pain tearing through his arm not as heat, but as absolute, paralyzing frost. It felt as though someone were ramming a rusted iron bar down through his wrist, splintering the carpal bones into chalk.
He stayed on his knees, his forehead pressed against the cedar baseboard, his breath coming through his nose in short, whistling gasps.
Ten heartbeats. Twenty.
The sizzling died to a faint hiss.
Corin pulled his hand back. He spat a thread of red saliva onto his trousers.
The silver-leaf had sunken straight into the cut. The edges of the wound had puckered shut, sealed not with a scab, but with a hard, metallic seam that looked like tarnished solder. The black thread in his vein was gone. In its place, running from his thumb to his inner wrist, was a pale, silvery scar, stiff and raised, completely devoid of hair.
He tried to flex his fingers.
His thumb moved an eighth of an inch, then locked. The joint was rigid. He had to force it with his left hand, the cartilage clicking like a poorly geared rat-wheel. The rot had stopped, but the metal had welded the tendon to the sheath. He would never hold an engraving burin with that hand again.
Corin picked up the lead lid and screwed it back onto the jar.
His shoulder knocked against a wooden crate shoved beneath the lowest shelf. The lid of the crate was unnailed, held closed only by a strip of gummed paper.
Corin paused.
The paper was labeled in purple ink: *For disposal – Property of the late Regulus Black, 1979.*
Corin looked at the label. Then he looked at the floorboards near the front of the crate.
There were fresh scrape marks in the dust. Someone had pulled the box out within the last forty-eight hours, and they had not been careful with the brass corners.
Corin used the tip of his penknife to slice through the gummed seal. He lifted the cedar lid.
Inside lay three velvet pouches, their fabric moth-eaten and bald, and a shallow tray of jeweler's sawdust. The tray was empty, save for an indentation where a heavy, rectangular object had rested for years. Beside the hollow lay a pair of bone-handled nippers and an empty glass phial with a dried, chalky crust at the bottom.
Corin picked up the phial. He brought it to his nose.
It smelled of bitter almonds, sulfur, and the sour grease of carbolic soap.
Draco had not just stolen from Corin's trunk. Draco had been in this cupboard. He had taken whatever lay in that tray, and he had used Slughorn’s bone-handled nippers to cut it.
A hinge groaned in the front office.
Corin dropped the phial into the sawdust, lowered the lid, and slid the crate back under the shelf with his boot.
He pulled the velvet curtain aside half an inch.
The outer office was no longer empty.
Professor Slughorn stood by the coal grate, his heavy silk dressing gown trailing green tassels across the hearth rug. His bald head gleamed with sweat, despite the early hour. He was not alone.
In the armchair opposite the sofa sat Blaise Zabini.
Blaise was fully dressed in his school robes, his silver-trimmed tie knotted with his customary, flawless symmetry. His hands were folded over his knees. Between his feet sat a small, square case of polished morocco leather, fastened with a silver clasp shaped like an owl's claw.
"You are quite certain your mother has no further use for it?" Slughorn asked. His voice was low, wet around the vowels, carrying the nervous tremor of a man handling stolen plate. "The provenance is... delicate, Blaise. If the Ministry were to inquire after the estate's liquidation—"
"My mother has married seven times, Professor," Blaise said smoothly. His voice had the flat, unhurried cadence of someone reading out grain prices. "She does not keep ledgers for men who die of heart failure in Venice. The cabinet in the palazzo had two keys. She gave one to the bailiff. She gave the second to me."
Slughorn wiped his upper lip with a lace handkerchief. "And the wood? It has not warped?"
"The walnut is sound," Blaise said. "Though my mother’s cousin in Naples insisted the interior smelled of vinegar before they crated it. He said the hinges were singing."
Corin pulled his head back into the darkness of the store cupboard.
His heart thumped hard against his ribs, but his face remained stone-cold.
*Two keys.*
Borgin and Burkes had never owned the pair to the Hogwarts cabinet. His uncle had lied. Caractacus had bought one half from an estate sale in Whitechapel and assumed the twin was rotting in a ditch in Wiltshire. But Lucius Malfoy hadn't moved a cabinet out of Wiltshire two winters ago; Lucius had moved *money*. He had bought the Italian twin through Zabini's mother before his arrest, and Draco had spent the autumn trying to bridge a passage between Scotland and an attic in Surrey that was already being dismantled by Ministry inspectors.
Draco was working on the wrong door.
Or worse—the door he was singing to had three ends, not two.
"Take the port, Blaise," Slughorn was saying, his voice drifting through the velvet curtain followed by the clink of crystal. "A small glass. To seal the understanding. We shall have the estate papers processed through my cousin at the Department of Magical Logistics by noon."
"I don't take fortified wine before breakfast," Blaise replied. "Leave the paperwork with the owl post. And Professor?"
"Yes, my boy?"
"Tell your friend in the headmaster's tower that Draco has stopped taking his meals in the Great Hall. It makes the others nervous. Theodore has started carrying an iron bodkin in his sock, and Goyle is sleeping with his boots on."
Silence fell over the outer room, save for the dry, fluttering sound of Slughorn’s breath.
"He is under... considerable strain," Slughorn whispered.
"He is clumsy," Blaise corrected. "There is a difference."
Corin backed away from the curtain. He reached the narrow ventilation grate set into the foundation wall behind the fourth shelf—the old flue that led down to the drainage tunnels beneath the lake. The iron grill was loose; his grandfather had used it fifty years ago to haul contraband salamander blood out of the castle cellars.
He worked the catches with his good left hand.
The metal groaned, but the coal fire in the other room masked the sound. Corin slid through the gap feet-first, his boots finding the slimy ledge above the lower culvert.
He pulled the grill shut above him.
He hung in the dark for five seconds, the icy reek of lake water and ancient limestone filling his lungs, his right arm dangling useless and silver-stitched at his side.
Ten o'clock tonight. Boris the Bewildered.
Corin Burke dropped into the dark.
When his boots struck the stone of the culvert floor, his numb right thumb caught on the rough granite of the wall. The joint didn't bend. It didn't tear. It rang against the wet stone like an iron nail, cold and hollow, completely separated from the boy who carried it.