The roar began before dawn. That low shaking thrum sounded like an avalanche grinding down a distant canyon.
Giles stood on the newly crowned southern road, his transit level mounted on its tripod. Through the brass optic, he watched the River Skell.
The black water had risen three feet in four hours. It was no longer carrying clear mountain froth. It was a boiling torrent of gray mud, snapped pine trunks, and grinding chunks of ice-blue ice.
“The northern ice dams are breaching,” Kenneth Drake said, leaning against his pacing rod. “The tremors Maeve heard. When glaciers crack, the meltwater lakes behind them let go all at once. If that surge hits this bend, it will undercut the road and scour the stockade foundations into the gorge.”
Giles pulled his notebook from his pocket, checking the high-pressure cross-section.
“River bend curve is thirty-two degrees,” Giles said. “The outer bank absorbs outward-pulling high-pressure sideways tearing force of seventy pounds per square foot during peak flood stage. Soaked clay can’t resist that shear speed. It will slough off in twenty-ton chunks. We need an energy-draining away riprap stone retaining wall.”
Kenneth frowned, staring down at the churning brown water. “Riprap? Dumping rocks in the water?”
“Not dumping rocks,” Giles said. “Dumping rocks is an unengineered waste of material. Rounded river cobbles wash away under three knots of current because they lack clockwork interlock. We need angular blasted granite from Duncan’s quarry. Minimum weight two hundred pounds per stone. Angular faces interlock under water pressure, creating a flexible armor layer that dissipates ninety percent of the current’s striking force.”
Captain Kroll marched up with thirty tunnel diggers, their iron pry-bars clanking on their shoulders. “The quarry sledges are loaded, Lord Giles. Master Duncan sent down forty cartloads of fresh granite spoil from the upper ledge.”
“Set the toe trench,” Giles commanded. “Excavate a two-foot trench along the river waterline. The heavy stones must seat below the scour line. Or the current will undermine the armor from beneath.”
Before the first stone was tipped into the river, Giles had walked the corner of the stockade with Kenneth Drake. He drove iron probe rods into the bank.
“Look at the sub-surface moisture migration,” Giles said, pulling the rod free. The iron tip came up coated in gray, soupy clay. “The river isn’t just eroding the bank from the outside. It’s exerting pore-water pressure from within. When the water table rises, the soil loses its shear pushback. If that corner wooden wall post slips six inches, the narrow high walkway collapses like a house of cards.”
“The wooden wall was built on green spruce posts driven four feet into the dirt,” Kenneth said. He tapped the corner castle wall with his pacing rod. “In a normal winter, four feet is enough to hold against infantry.”
“A river flood isn’t infantry, Kenneth,” Giles replied. “Water exerts a water-pressure lateral thrust of sixty-two point four pounds per cubic foot. You combine that with five miles per hour of river-bed speed. Then, an unarmored clay bank dissolves in minutes. We must protect the toe of the slope before the water-pressure head reaches peak level.”
* * *
Master Duncan Stone-Splitter himself arrived with the second stone train, his wire-mesh goggles pushed up on his forehead. The dwarf carried a twenty-pound steel dressing hammer, inspecting the granite blocks loaded on the timber sledges.
“Biotite granite,” Duncan rumbled, striking a block with a ringing tap. “Clean tetrahedral fractures. When water hits these sharp edges, it breaks its own back. Lowlanders usually throw soft limestone or round river stones into a wash. Then wonder why their bridges drown. This rock will stand until the mountains crumble.”
“The shape must be precise, Duncan,” Giles said, showing him the slope profile. “A two-to-one incline. If the slope exceeds thirty degrees, the stones will roll under water-flow drag. Toby, set the slope guide.”
Toby Karr planted two wooden batter boards along the bank, connecting them with a taut yellow cord that marked the thirty-degree grade.
“Batter boards set, Lord Baron,” Toby called out. “Two-to-one slope marked true.”
Down in the icy shallows, Bram and fifteen tunnel diggers waded into the freezing mud wearing greased leather boots.
The cold was brutal. Water splashed over their knees, crusting their trousers in stiff ice, but the men worked with desperate strength. They used iron pry-bars and timber rollers. They wrestled the massive two-hundred-pound granite boulders into the excavated toe trench.
Each jagged block seated into the muck with a heavy, sucking thud, locking against its neighbor like pieces of an ancient stone puzzle.
Behind the heavy granite armor, Dob sat on his wooden stool with his cane, overseeing the filter blanket.
“No clay behind the stones!” Dob shouted to the barrow-men. “Clean pea gravel only! The Lord Master builder says if you put mud behind the armor, the river will suck the bank right through the cracks! Keep the gravel clean!”
A steady line of wheelbarrows dumped graded river gravel into the void behind the boulders. The porous gravel acted as a geotextile filter. It allowed groundwater to drain freely into the river while preventing fine soil specks from piping out.
Sister Teresa walked the upper terrace with a wooden pail of wet lime plaster slurry. She splashed the white wash over the exposed stone joints, her lips moving in silent prayer.
“Hold the flood in its place, holy stone,” Teresa murmured, her woolen habit whipped by the rising gale. “Be the shield of the righteous.”
By mid-afternoon, one hundred and fifty yards of armored granite stone retaining wall lined the outer curve of the River Skell.
In the sick room tent, Sister Teresa worked over the unconscious scout with focused urgency.
She stripped away Garrick’s frozen brigandine, revealing four jagged deep cuts across his left ribs. The flesh around the wounds was not red or inflamed. It was a pale, waxy indigo, rimed with delicate crystals of sub-zero blue frost that refused to melt in the warm air of the tent.
“Frost-rot,” Teresa murmured, her fingers trembling as she dipped a linen cloth into warm vinegar. “The venom of the cold. If the chill reaches his heart, his blood will turn to slush.”
Giles leaned over the cot, holding his brass magnifying lens.
“It’s not venom, Teresa,” Giles said. “It’s a heat-drawing crystal matrix that extracts heat energy from surrounding blood-vessel tissue. Pour warm boiled salt water over the wound. The sodium chloride lowers the freezing point of the water and dissolves the crystal-clear structure.”
Teresa obeyed. As the warm salt water touched the blue crystals, they hissed with a sharp, faint crackle. It melted into harmless clear water that ran off the linen into a copper bowl.
Garrick coughed weakly, his eyelids fluttering.
“Captain,” the scout whispered, his voice trembling. “They didn’t charge like beasts. They moved in ranks. The alpha stood on the ridge, its blue horns burning in the mist. It breathed... And when the white smoke touched our narrow high walkway, five men froze solid where they stood. Their bowstrings snapped like dry glass.”
Kenneth gripped the edge of the cot, his face grim. “Sub-zero breath. An organic ice-cold projector.”
“A heat-powered shock weapon,” Giles corrected, pocketing his lens. “If the heat differential is extreme, wood and steel become brittle. We’ll need heat countermeasures on the castle walls before the assault begins.”
* * *
Then, from upriver, a thunderous crash shook the gorge walls.
A wall of gray water, four feet high and choked with splintered logs and grinding blue ice, rounded the bend at twenty miles an hour.
“Surge incoming,” Kenneth roared, waving his rod. “Clear the bank. Everyone to the road.”
The workers scrambled up the gravel slope just as the flood struck.
The wave slammed into the outer curve with the sound of a collapsing castle. Thousands of tons of churning, debris-laden water smashed directly against the newly laid granite stone retaining wall.
Spray exploded thirty feet into the freezing air, showering the road in icy mist. Heavy hemlock trunks hammered against the stones with gunshot cracks.
For three terrifying minutes, the river boiled over the rocks in a foaming fury.
Then the building proved its design.
The angular granite blocks didn’t shift an inch. The linked jagged faces broke the striking force of the current, shattering the wave into tumbling white foam that deflected smoothly down the center channel.
The road behind the stone retaining wall remained fully dry. The stockade wooden wall stood firm on its shale knoll, undisturbed.
The settlers gathered along the road in stunned relief.
“The stone held,” Toby breathed, wiping spray from his glasses. “It didn’t move a finger.”
“Angular aggregate interlock,” Giles noted calmly, entering the data into his book. “Standard high-pressure energy fading away. Kenneth, inspect the toe line for scour settlement.”
Before Kenneth could move, an exile named Joram pointed down into the receding foam near the lower eddy.
“Someone is down there,” Joram shouted. “Clinging to a spruce log.”
Kenneth and Kroll sprinted to the water’s edge, sliding down the wet riprap with drawn daggers.
Wedged between two granite boulders was the shattered trunk of a hemlock tree. Tangled in the branches was a man, his leather brigandine shredded, his bare arms sliced open and purple with cold.
They cut him free and hauled him onto the dry road.
The man was bleeding from deep, frozen gouges across his ribs. Claw marks, four inches wide and rimed with crystal-clear blue frost. He coughed up black water, his teeth chattering wildly.
Kenneth knelt beside him, wrapping him in a dry wool cloak. “I know this man. He’s Garrick, a guard post scout from the frontier settlement of Black Mire, ten miles north.”
Garrick’s eyes opened, rolling in blind panic. He grabbed Kenneth’s sleeve with stiff, blackened fingers.
“The... The wolves,” Garrick choked out, blood frothing on his lips. “They didn’t just attack. They walked through our wooden wall like smoke. Five hundred beasts, Captain... Five hundred of them. Black Mire is gone. Every cabin burned to ash.”
He stared up at Giles with wild, hollow eyes.
“They’re marching south,” the scout gasped before slumping into blackout. “They’re coming for Rustgate.”
Kenneth looked up at Giles, his face as gray as the winter sky.
“Five hundred beasts,” Kenneth whispered. “They broke a fortified settlement in a single night.”
Giles closed his notebook with a soft click. “Then we have forty-eight hours to complete our storage and munitions. Toby, help carry the scout to Teresa. We have work to do.”