The Lock-Keeper's Backward Current

• Chapter 1 The Final Slack-Water
• Chapter 2 The Gallows Above the Weir
• Chapter 3 The Preacher's Ledger
• Chapter 4 November Frost on the Towpath
• Chapter 5 The Bargeman’s Missing Cargo
• Chapter 6 Silt in the Culvert
• Chapter 7 An Intercepted Signal at Lock Nine
• Chapter 8 Autumnal Iron
• Chapter 9 The Sinking of the Black Heron
• Chapter 10 Counter-Weight and Cipher
• Chapter 11 The October Inquest
• Chapter 12 Lanterns in the Mist
• Chapter 13 Mud and Munitions
• Chapter 14 The Canal Inspector’s Bribe
• Chapter 15 A Knife in the Sluice
• Chapter 16 Midsummer Low Water
• Chapter 17 The Lock-House Parlour
• Chapter 18 Whispers in the Basin
• Chapter 19 The Forged Manifest
• Chapter 20 June Floods
• Chapter 21 The Courier from Whitehall
• Chapter 22 The Water-Marked Sovereign
• Chapter 23 Spindle and Key
• Chapter 24 The First Sluice-Gate
• Chapter 25 Spring Thaw at the Basin
• Chapter 26 The Upstream Commission

The rope around Silas Thorne’s neck smelled of Stockholm tar and damp hemp, a familiar scent to a man who had spent thirty years tending the timber gates of Lock Nine. It was six o’clock on a freezing December morning, and the gray mist rising from the cut had swallowed the spectators gathered at the edge of the canal basin. They were mostly boatmen, towpath vagrants, and a few silent men in wool coats who kept their hands buried deep in their pockets. Silas stood on the wooden trapdoor of the gallows erected beside the masonry of the upper chamber, his boots resting on the very oak planks he had scoured clean of moss only three months prior.

The executioner, a rotund man brought by the night coach from Gloucester, fumbled with the knot behind Silas’s left ear. He was sweating despite the frost that coated the ironwork of the lock beams.

"You’ve a quiet crowd today, Master Thorne," the executioner muttered, his breath coming in white plumes. "Usually they throw turnip tops or sing a psalm."

"They’re waiting for the water to clear," Silas said. His voice was raspy, dry from two days in the unheated cell beneath the gaol house, but it carried across the still basin. "The silt always settles at the drop."

The magistrate, standing on a makeshift platform resting on a coal barge, unfolded a thick sheet of parchment. His spectacles were fogged from his breath, and he wiped them twice on his velvet sleeve before reading the sentence. The charges were read aloud to the shivering crowd: high treason against the Crown, the unlawful interception of government dispatches, complicity in the destruction of His Majesty’s Ordnance barge Black Heron, and the murder of an officer of the Inland Revenue.

To the canal folk, the words meant little. To them, Silas Thorne was simply the man who took their tolls, greased the paddle spindles, and kept the upper reach from draining into the valley during the summer drought. They knew he was a sullen man who kept a lean black dog and rarely bought ale at the Swan with Two Necks, but they did not know him as a traitor. They only knew that since his arrest three weeks ago, the water levels had been erratic, and the lower gates were leaking badly at the heel-posts.

Silas did not look at the magistrate. He looked past the scaffold, down the long, straight cut of the Grand Union toward the eastern bend. The water was dead calm, a sheet of dark lead reflecting the leafless willows. In the high summer, the cut would be thick with duckweed and the sharp, oily reek of coal tar, but today it was cold and pure. Upstream, three miles past the aqueduct, lay the high ridge where the telegraph towers stood. Downstream lay the garrison town and the salt marshes. Lock Nine sat precisely between them, the narrow throat through which everything passed—coal, iron, grain, and the thin paper slips tucked inside the hollow iron bolts of the timber barges.

"Have you any last words, prisoner?" the magistrate asked, folding the parchment with a sharp snap. "Any repentance for the blood shed upon this waterway?"

Silas shifted his weight. His knees were stiff from the rheumatism that plagued every lock-keeper by their fiftieth year. "Check the lower sluice," he said to no one in particular. "The chain is twisted on the windlass. If you drop the gate hard, it’ll crack the sill."

The executioner pulled the black hood over Silas’s face, plunging the world into a warm, coarse dark that smelled of old flour.

There was a heavy, metallic clank as the bolt was struck back. For a single, suspended second, Silas felt the weight of his own body floating above the cut, free of the mud, the grease, and the constant, demanding roar of the sluices. Then the floor gave way, the hemp snapped taut, and the water carried its secrets away.

Two hours after the trapdoor fell, the crowd had dispersed into the taprooms of the basin, leaving only the frost and two parish constables tasked with guarding the body until the coroner’s cart arrived.

Inside the lock-house, the coal fire had long since gone out. The small, square building sat on a narrow tongue of land between the canal and the overflow weir, built of rough-hewn limestone with a slate roof that dripped continuously into a rain butt. The front room was bare except for a rush-bottomed chair, a pine table, and a cast-iron stove. On the wall hung the printed tide tables for the Severn estuary and a brass-bound clock that had stopped at four minutes past five—the exact moment the high constable’s men had breached the door three weeks earlier.

Mr. Jasper Vance, an assistant investigator from the Home Department, sat at Silas Thorne’s table with his collar turned up against the draft. He was a thin man in his thirties, with fingers stained purple from ink and eyes that blinked constantly against the light. Before him lay the contents of Silas’s pockets, cataloged on a sheet of blue foolscap: three copper halfpence, a horn-handled pocket knife with a broken blade, a lump of sheep tallow used for waterproofing boots, and a heavy brass key with five notches cut into its flag.

"It doesn’t add up," Vance said, rubbing his temples.

Across the room, Constable Higgins was poking at the cold ashes in the grate with the tip of his boot. "What doesn't, sir? The man’s hanged. The rope was short enough, didn't tear his head off. Proper job, I'd say."

"The money," Vance said, tapping the blue paper. "A man who sells government intelligence to foreign agents for six months does not die with three halfpence in his breeches. He was paid in gold sovereigns—minted in 1841, marked with a tiny cross on the die-mark. We found eighty of them buried in a butter tub at the bottom of the coal cellar. Where is the rest?"

"Drunk, most likely," Higgins offered. "Or dropped in the cut. You drop a purse in twelve feet of silt at Lock Nine, you won't see it again till the Last Judgment."

"Thorne didn't drink," Vance said softly. He stood up and walked to the small square window that looked out over the lock chamber. Below, the water was dark and thick. "And he didn't drop anything by accident. Every movement that man made was recorded in his logbook for fifteen years. He noted every barge, every ton of pig iron, every barrel of whale oil. He noted the wind direction four times a day. A man like that does not lose his wages in the mud."

Vance reached out and touched the window frame. The wood was soft, rotting from the perpetual dampness of the weir. He ran his thumb along the sash until he felt a slight groove in the timber—a mark made not by the builder, but by the frequent passing of a fine cord over the sill. He opened the sash and looked down. Directly beneath the window, six feet below the sill, the cold water of the canal lapped against the stone wall of the lock-house.

"Bring the rake," Vance ordered, turning back to the room.

"Sir?"

"The drag-rake from the tool shed. The one he used for clearing dead sheep and tree branches from the sluice grate."

Higgins grumbled but stepped out into the fog. Vance remained by the window, his coat tail flapping in the cold draft. He looked out at the gallows, where Silas Thorne’s body still hung, swaying slightly whenever a gust of wind came down the reach.

To the casual observer, the case against Silas Thorne was closed. The evidence gathered in late November had been overwhelming: the forged clearance papers found in the desk, the dead Revenue officer dragged from the weir with a fractured skull, and the intercepted letter detailing the horse-artillery movements at Portsmouth. The trial at the autumn assizes had taken less than three hours.

Yet Vance was not satisfied. He knew how espionage worked along the inland waterways. A lock-keeper was not a master mind; he was a gatekeeper, a node in a network that stretched from the ironworks of Birmingham to the docks at Bristol. Silas Thorne had been the plug in the bottle. Now that the plug had been pulled, the water was beginning to run backward, and Vance needed to trace the current to its source.

Higgins returned, lugging a heavy iron rake with seven curved prongs attached to a twenty-foot ash pole. Drops of muddy water splashed onto the flagged floor as he leaned it against the table.

"Where do you want it shoved, Mr. Vance?"

"Out this window," Vance said. "Lower it straight down against the wall. Tell me if you feel anything other than stone."

Higgins grunted, hoisted the pole, and extended the rake out into the freezing air. He lowered it until the iron tines broke the surface of the water with a dull plop. He let the pole slip through his hands, inch by inch, scraping the masonry.

"Nothing but slime," Higgins said after a moment. "It’s smooth stone all the way to the bottom ledge."

"Work it sideways," Vance instructed, leaning out beside him. "Near the corner where the house wall meets the lock masonry."

The constable dragged the pole back and forth. The iron tines scraped against the ashlar blocks with a hollow, grinding sound. Then, with a sudden jerk, the pole stuck.

"Got something," Higgins muttered, leaning his weight against the wood. "Feels like a tree root. Or an old chain."

"Don't pull hard," Vance said sharply. "Lift it slowly. If it's a line, you'll snap it."

Higgins worked the pole with surprising delicacy for a man of his build. He lifted the rake inch by inch out of the black water. As the prongs emerged into the cold air, Vance saw a thick loop of oiled tarred twine hooked over the central tooth. Suspended from the twine was a small, heavy object wrapped in oilskin and bound tight with lead wire.

Vance reached out, seized the bundle, and cut the cord with Silas’s pocket knife. He carried the dripping package to the table, sweeping the blue foolscap paper to the floor. Higgins stood by, wiping his wet hands on his trousers, his breath heavy in the small room.

Vance unpeeled the layers of stiffened canvas. The oilskin was slick with fish fat to keep out the moisture. Inside was not gold, nor a cipher book, nor a list of names.

It was an ordinary leather-bound pocket diary, worn smooth at the corners, its cover stained with green river mold. On the flyleaf, written in a precise, copperplate hand that belonged to a man who measured his life in inches of water, was the name: Silas Thorne, Keeper, Lock Nine. 1845.

Vance turned the book over. The entries did not begin at the front. The latest entry, dated November 28th—the day of Silas’s arrest—was written on the very last page.

28 Nov. Vance read silently, his eyes scanning the narrow lines. Wind NW. Frost holding. Water three inches low on the upper sill. No boats passed after noon. The red-headed man from the ironworks did not show. Left the key under the fifth flagstone as agreed. They are coming up the path now with the warrant.

Vance flipped back one page. The date was 27 Nov.

27 Nov. Wind W. Rain at dusk. Coal barge 'Mary Jane' passed down with forty tons. Paid three shillings toll. Signal given at the bridge: two oil lamps in the upper window. The crate of brass fittings was removed from the hold while she was in the chamber.

Vance stopped. He looked up at the quiet, frozen cut outside the window.

The diary was not a record of what Silas Thorne had done leading up to his crime. It was a reverse log. Every entry moved backward in time, day by day, vessel by vessel, secret by secret. Silas had recorded the network not as a grand conspiracy, but as a daily schedule of water, weight, and silent transactions.

"What is it, sir?" Higgins asked, leaning over the table. "Is it the names of his friends?"

"It is the map," Vance whispered, turning back to the entry for November 26th. "He didn't start this in the spring. He built it backward from the day he knew he was caught. Every step he took to build his trap is written here, starting from the end."

Vance closed the book. The leather was damp, cold as the mud at the bottom of the chamber. Outside, a loud splash echoed across the basin—the coroner’s men had arrived, and the long, stiffened shape of Silas Thorne was being cut down from the beam above the weir. The rope groaned, the timber creaked, and then there was only the sound of the water slipping silently through the narrow gap in the upper gate, flowing steadily down toward the sea.

The coroner’s wagon had wheels that shrieked like stuck pigs. It was a narrow, high-sided cart painted the dull yellow of curdled milk, and its pony had the rickets. The driver, an elderly parish pauper named Gidley whose knuckles were swollen the size of walnuts, did not bother to climb down from the bench. He merely backed the cart toward the masonry approach until the iron-rimmed wheels bumped hard against the oak balance beam of the lower gate.

"Fell clean, did he?" Gidley asked, staring down at the bundle that lay on the frost-bitten turf beneath the timbers. The body was rolled in a strip of greasy sailcloth that had seen better days hauling manure out of the slaughterhouse wharves.

Higgins spat into the basin. "Clean as an axe-stroke. Broke his neck before the drop was half finished. Silas Thorne was never a heavy man, but he was all sinew and grit. Put up more of a jar than you’d expect."

Jasper Vance ignored the boatmen and the constabulary banter. He stood at the timber apron of the weir, the damp leather diary tucked inside the breast pocket of his coat, resting hard against his ribs like a slab of cold river slate. The overflow weir at Lock Nine was an ingenious piece of stonework, constructed forty years prior when the canal company had blasted out the sandstone spine between the upper reach and the river tributary below. A broad curved lip of dressed millstone grit allowed the excess head of water to tumble thirty feet down a stepped cascade, churning itself into yellow-brown froth before slipping quietly into the marshy reedy bottom of the lower valley. The sound here was never silent; even when the lock gates were shut fast and the basin slept, the weir hissed like a nest of adders.

Vance watched two parish men hoist Silas’s corpse into the bed of the wagon. The man’s boots, cobbled with thick iron nails that had scratched decades of white lines into the lock stonework, hung out over the tailgate. One sole was worn straight through to the leather inner, patched with a lead seal of the kind the Birmingham wire manufacturers used on their crates. Vance made a mental note of that patch. A lock-keeper did not mend his footwear with industrial lead unless he had lead to waste and an iron punch to flatten it.

"Mr. Vance, sir," called Higgins, leaning on his ash rake as though it were a shepherd’s crook. "The crowner wants to know if he’s to take him to the cellar under the vestry at St. Jude’s, or if you want him laid out at the Swan."

"The church cellar," Vance said without turning around. "The publican at the Swan has three cousins working the lime boats from Dudley. We don't need fifty boatmen drinking small beer over Silas Thorne's cold liver before I've had the surgeon go through his hair with a comb."

Higgins frowned, his jowls quivering in the freezing wind. "His hair, sir? What would an old cut-throat have in his whiskers?"

"Ink," Vance replied shortly. "Or phosphorus. Or nothing at all. Tell the driver to move. And tell him to take the gravel track, not the towpath. If that pony slips into the upper reach, we'll spend all afternoon fishing the deceased out of his own reservoir."

Gidley cursed at the beast, whipped the reins across its bony rump, and the yellow wagon trundled away toward the lane, its axle squealing with every revolution.

Vance turned back to the lock-house. The timber scaffold, erected by two carpenters from the borough gaol the previous evening, seemed ridiculously oversized for its purpose. It was made of raw pine baulks, smelling of resin and wet sawdust, lashed together with two-inch hemp. It stood directly over the weir's stone culvert, so that any bodily evacuation or dropped possession might fall straight into the racing spillway and be carried out to the marsh before the spectators had finished their morning prayers. It was an arrangement Vance found distasteful, not out of any tenderness for Silas Thorne, but because water was the enemy of evidence. Water washed clean; water rusted steel; water dissolved the saltpetre and gall that gave paper its memory.

He climbed the wooden ladder to the scaffold platform. The trapdoor was hanging down on its heavy iron butterfly hinges, swinging an inch or two in the gusty wind that blew off the marl pits to the north. Vance knelt on the edge of the opening, his trousers soaking up the muddy slime left by the executioner's greasy boots.

He looked down into the dark chamber beneath the drop. It was not a pit dug in the earth, as was common in the county gaol yards, but a square brick shaft that opened directly onto the masonry conduit of the weir. Ten feet below the trap, the stone floor of the sluice sloped down at an angle of thirty degrees. Water was washing over it now—a thin, glassy skin an inch deep, escaping through a warped paddle board in the sluice frame.

Something white caught his eye against the dark moss of the brick wall.

It was caught on a projecting iron spike, one of the rungs the canal masons had driven into the lime mortar when the chamber was pointed in '38. Vance lay flat on his stomach, reached his right arm down into the gap, and strained his fingers. His fingertips brushed cold, wet paper. He extended his reach, his shoulder joint clicking against the pine framing of the trap, until he managed to pin the scrap against the rusted iron with two fingers and work it loose.

He drew it up into the pale December daylight.

It was not a letter. It was an ordinary railway receipt, torn diagonally across its text, from the London and Birmingham line at Curzon Street. The date stamped in faint blue ink was 25 November 1845—three days before Thorne’s arrest. The line of print that remained legible recorded the carriage of two crates of Hardware, wrought, sundry consigned to a Mr. T. Finch, care of the Wharfinger at Lock Nine. On the reverse, written in the same steady copperplate hand Vance had found in the diary, was a single column of figures:

38-14-2
14-0-0
52-14-2
less 4s. toll for lime.

Underneath the calculation was a small, crudely drawn mark: an anchor crossed with a boat-hook, the traditional sign of the Severn barge-masters, but with three dots pricked into the triangle of the fluke with the point of a needle.

Vance stood up and blew the grit from his fingers. "Finch," he muttered. There was no Finch on the canal company’s payroll, nor had any man of that name appeared in the depositions taken before the grand jury at the Shire Hall.

He walked down from the scaffold and returned to the quiet interior of the lock-house. Constable Higgins was still outside, bellowing at two urchins who had crept along the lower towpath to throw stones at the scaffold timbers. Vance pulled the heavy oak door shut, dropping the iron latch into its keeper. The sound of the wind and the hiss of the weir dropped to a low, rhythmic mutter, like the breathing of some monstrous bellows hidden beneath the floorboards.

He laid the leather diary on the table and pulled the rush-bottomed chair close to the cold stove. He did not open the book immediately. Instead, he took from his waistcoat pocket a pair of brass calipers and a small ivory rule he had bought from an instrument maker in the Strand. He measured the spine: six inches by three and a half, precisely the size of the pocket-books issued by the Grand Junction Canal Company to its district superintendents, yet this one had no company crest stamped into the pigskin. The leather was plain, scuffed, and stained with the distinctive black grease that came from the winches of the Birmingham iron boats.

Vance turned the book to the entry that preceded the date of Thorne's arrest: November 27th.

Silas had written with an iron-gall ink that had bitten deep into the wood-pulp paper. The script was methodical, without flourish, the letters upright and rigidly spaced, like the teeth of a rack-and-pinion gear.

27 Nov. Wind W. Rain at dusk. Coal barge 'Mary Jane' passed down with forty tons. Paid three shillings toll. Signal given at the bridge: two oil lamps in the upper window. The crate of brass fittings was removed from the hold while she was in the chamber. Delivered to the dry-arch under the turnpike. The driver was the lad with the harelip from Stourbridge. Paid him eighteen pence. Upper gate leaking four inches an hour at the heel-post. Replaced the leather gasket on the lower paddle.

Vance read it through twice. He leaned back and looked at the brass-bound clock on the wall, its pendulum frozen at the hour of Silas’s capture.

The Mary Jane was known to him. She was an old wooden fly-boat, built at Tipton in the twenties, owned by a widow named Cleary who lived in a brick hovel near the salt works at Droitwich. When the Inland Revenue officers had searched the canal basin three weeks ago, the Mary Jane had already cleared downstream toward the Severn, carrying nothing more suspicious than forty tons of Cannock coal and three barrels of salted herrings. The searchers had found no brass fittings, no crates, and no lad with a harelip. They had concluded that the tip given by the excise spy had been erroneous—one of the dozens of false alarms that plagued the district during the autumn panic.

Yet Silas had noted it with the same indifference he gave to the leaking heel-post. To Thorne, the transfer of a crate from a barge hold to an arch under the turnpike road was an operation no more remarkable than replacing a leather gasket on a sluice paddle.

Vance turned back another page. The date was 26 Nov.

26 Nov. Wind SW, backing to S. Gale toward nightfall. The Inspector’s gig arrived at four. Mr. Gedge stayed twenty minutes. He did not look at the toll book. He took the tin canister from the tea-caddy and put six sovereigns on the shelf behind the clock. He said the cavalry were moving two squadrons from Coventry to Gloucester by the south road on Friday. Told him the bridge at Lock Eleven was weakened by the high water and would not take the six-pounder guns. He said the boats would carry the shot instead. The 'Swan' had two casks of pale ale delivered from the brewery at Stone.

Vance’s pulse quickened. He stood up and walked to the clock. He had searched the case himself three weeks ago, finding nothing inside but the iron weights and the dusty carcass of a field mouse. Now he reached behind the clock body, feeling along the narrow gap between the mahogany case and the damp lime plaster of the wall.

His fingers met the rough edge of a ledge. It was not a purpose-built shelf, but the top of an oak lintel that spanned the old fireplace before the cast-iron stove had been inserted in the opening. Silas had known the house to its bones; he had lived here alone since the year the Queen came to the throne, through the cholera summer and the winter when the frost had locked the cut in nine inches of iron ice for eleven weeks.

Vance ran his fingernails along the grime of the lintel. Behind the left-hand corner of the clock, his fingers touched something hard and metallic that rolled slightly under his touch.

He drew it out. It was not a sovereign. It was a brass token, no larger than a shilling, stamped on one side with the head of a fox and on the other with the numeral 7. Through the centre of the token a small square hole had been punched, its edges burred from the smith’s cold-chisel.

"Gedge," Vance said softly.

Arthur Gedge was the Chief District Inspector for the canal company, a man who wore a beaver hat and carried a gold-topped cane, whose signature appeared on every toll-sheet and timber requisition from Wolverhampton to the mouth of the Avon. Gedge had been one of the three magistrates sitting on the bench when Silas was committed for trial. He had sat with his thumbs hooked in his waistcoat pockets, nodding gravely as the Crown prosecutor laid out the details of the treason. He had even offered a few words of commiseration to the court on the difficulty of finding honest servants among the water-folk, who were, he had observed, "by nature nomadic, drunken, and indifferent to the security of the realm."

Vance slipped the brass token into his waistcoat with the torn railway receipt. The pattern was beginning to show its grain, like a piece of oak pulled from the peat moss. Silas Thorne had not been an isolated traitor selling secrets to French or Russian agents for pocket money; he had been the clearing-house for a traffic that involved the very men who maintained the highway. The canal was not merely a ditch of dirty water; it was an artery that ran through the industrial belly of the country, moving thousands of tons of pig iron, carbines, powder, and boiler plate without the noise or the telegraph wires that guarded the iron railways.

The lock door groaned and swung inward. Constable Higgins entered, his cheeks purple from the wind, carrying a steaming earthenware jug that smelled powerfully of stale beer and roasted ginger.

"Publican at the Swan sent it over," Higgins said, kicking the door shut with his heel. "Thought you might want something to cut the fog out of your throat, sir. He's asking if the cut’s to be opened for the two o'clock traffic. There's four coal flats backed up at the lower basin already, and the boatmen are beginning to use their whips on the towpath boys."

Vance looked at the logbook. "What boats are they?"

Higgins took a swallow from the jug, wiped his mustache with the back of his sleeve, and squinted toward the window. "The Dolphin, out of Tipton with forge-blocks. The Brothers, with red bricks from the Stourbridge kilns. And two narrowboats from the salt company at Stoke Prior. Nothing out of the way. Just the usual muck."

"Tell them the cut remains closed until the three o'clock tide," Vance said.

"They'll swear, Mr. Vance. They're losing their turn at the Gloucester river locks if they miss the afternoon head."

"Let them swear," Vance replied. "They can drink at the Swan until their money's gone. Then they'll be quieter when they pass the chamber."

He looked back down at the entry for November 26th.

He took the tin canister from the tea-caddy.

Vance crossed to the corner cupboard. The tea-caddy was still there—a cheap tin box japanned with red lacquer that had peeled into scales like the skin of a roach. Vance lifted the lid. It was empty save for three dried bay leaves and a pinch of dusty black bohea that had lost its scent years ago. But when he lifted the box, he felt a slight rattle beneath the false bottom.

He turned the canister upside down. With the point of Silas’s broken pocket knife, he pried at the seam near the base. The thin sheet-metal gave way with a screech, revealing a small circular cavity no thicker than two pennies.

Inside was a disc of thin, semi-transparent greaseproof paper, cut to the exact diameter of the tin.

Vance held it up to the gray light from the window. It was not written upon with pen. It was a rubbing, made with a soft graphite pencil over a metal plate or an engraving. It showed the line of the River Severn between Sharpness and Gloucester, with the various sand-spits and mud-banks marked with tiny letters. But the soundings were wrong. Where the official Admiralty charts marked five fathoms in the deep channel off Epney, this rubbing showed an obstruction—a bar of stone or sunken timber, marked with the words: Sill laid Oct 12. Four feet at neap.

Vance laid the greaseproof disc on the table next to the diary. "Silas Thorne didn't murder that Revenue man because of a dispute over toll-dues," he said to the empty room.

Higgins looked up from his jug, his small eyes widening. "Sir?"

"The Revenue officer, Miller. The one they found in the weir culvert with his brains beaten in with a windlass. The prosecution said he caught Silas taking bribes from the French timber boats."

"That was the story at the assizes," Higgins said. "Miller was a sharp lad. Used to search the horse-drawn flats for tobacco. Found two casks of Dutch gin under a load of Shropshire iron back in August."

"Miller wasn't looking for gin," Vance said. He tapped the greaseproof circle with the ivory ruler. "He was looking for this. Someone was measuring the depth of the Severn navigation at the low autumn tides. If you can sink two barges of furnace slag across the channel at Epney during a neap tide, you can cut Bristol off from the Midlands for three months. Not a pound of Welsh iron could reach the Ordnance works at Birmingham without going by rail, and the Great Western line doesn't have the rolling stock to carry the artillery contracts."

Higgins looked at the disc, then out the window at the weir. The water was tumbling down the steps, brown and white, roaring with the blind indifference of a river that cared nothing for governments or ironmasters.

"Silas Thorne did all that?" Higgins asked, his voice dropping an octave. "An old fellow who lived on bacon scraps and boiled turnips? He could hardly write his own name on the payroll sheet."

"He wrote well enough," Vance said, turning back another page in the book. "He wrote every day. And he didn't write for himself. He wrote for the man who was coming after him."

He paused, his eyes settling on the entry for November 25th.

25 Nov. Wind N. Hard freeze starting. The boat from the powder mills passed at midnight without lights. Lowered the water two feet to let her clear the low arch of the culvert. The tall man with the green spectacles was on the bank. He gave the word: 'The water goes back to the hills.' Gave him the four letters left by the carrier from Dudley. He said Miller had been seen at the basin with two constables from the city. Told him the lower culvert was dry if he needed to cross the marsh after the moon went down. He gave me twenty sovereigns. Put them in the tub with the rest.

Vance looked at the words: The water goes back to the hills.

It was a canal-man’s phrase, used when the locks were emptied in reverse during the winter maintenance to scour the gravel out of the upper ponds. But here it was a counter-sign.

Vance stood up, took his heavy woollen greatcoat from the peg by the door, and slipped his notebook and the greaseproof paper into his pocket. He picked up the heavy brass key with the five notches that had been found in Silas’s pocket on the scaffold.

"Where are you going, Mr. Vance?" Higgins asked, putting down his empty jug. "The coroner’s clerk said you had to sign the clearance for the body before the afternoon post."

"Let the clerk wait," Vance said, his hand on the door latch. "Silas Thorne is already dead. He’s the only man in this county who cannot run away, and he’s the only one who has left his tracks behind him."

"And the five coal boats at the basin?"

"Tell the boatmen to check their horses' shoes," Vance said. "We’re going down to the dry-arch under the turnpike. And Higgins—bring that ash rake. The day’s fishing isn’t done yet."

He stepped out into the freezing fog. Below him, the weir churned its endless yellow foam, and above the grey stone wall, the empty gallows stood like a pair of black shears against the winter sky, waiting for the water to rise.