The watchtower went up on the eastern bluff in less than eighteen hours. It was a crude, spindly thing made of stripped spruce poles, looking more like an oversized bird trap than a bastion of war, but it commanded the entire southern horizon. From its small, thatched platform, a man could see past the limestone notches of the pass and track the thin ribbon of the Oakhaven road until it dissolved into the grey pine forests of the lowlands.
At noon, Wat's apprentices hauled the old bronze bell up the muddy track, their boots slipping on the exposed roots. They hung it from a crossbeam of green oak with a double loop of greasy hemp rope. When they gave it a test strike, the single, clear note rolled down the throat of the valley, striking the stone face of the silver hill and bouncing back toward the Great Hall of Wheels like a physical blow.
Inside the keep's solar, the sound made the glass bottles on Thomas's shelf hum in sympathy.
Thomas didn't look up from his desk. He was sitting with his tunic thrown back over his chair, his shirtsleeves rolled to the elbow. The phone rested on a cedar block in front of him, its screen showing 72% battery. He was using a simple text editor to compile what he called the Argenton Assembly Code—a manual of basic drills, tactical formations, and administrative procedures for a town that was rapidly outgrowing its feudal skin.
"The brick-kiln is short three cords of seasoned ash," Victoria said, setting a heavy wood-bound ledger onto the table beside him. She smelled of the tallow grease they were using to seal the new water flumes, her fingers ink-stained from the scrip she had been signing since dawn. "The wood-cutters say they won't go into the southern groves while De Born's riders are thick in the brush. If the kiln cools down, the third row of worker cottages will stay half-walled until harvest."
"Tell the wood-cutters they go out in groups of six," Thomas said, his fingers clicking rhythmically against the glass screen as he saved his notes. "Two with axes, four with pikes from the forge. If they see a horseman, they don't run; they form a square against the timber and wait for the watchtower bell."
Victoria leaned over the desk, her eyes tracking the strange, blue symbols on his screen. "You are turning every laborer into a watchman, Thomas. They are grumbling in the lanes. They say they came here to escape the Baron's levies, not to be broken into ranks by a master weaver."
"The Baron's levy takes their grain and leaves them to rot in a ditch when the King goes to war across the sea," Thomas said, locking the screen. The sudden absence of the light left the room looking dimmer, greyed by the rain that was beginning to smear the windowpanes again. "Our watch keeps the roof over their heads. If they want the scrip to buy salt and iron, they pay for it with two hours of grease and clay every morning."
He stood up, his joints popping from hours of stillness. He felt an intense, localized exhaustion—not the physical weariness of the ditch-diggers, but the deep, neural fatigue of a programmer who had spent three days hunting a memory leak in a production environment. Except here, the memory leak was human fear, and the crash would mean a pile of ash where his factory stood.
He walked down the spiral stairs into the courtyard, where the air was thick with the bitter, chemical smell of the tanning pits and the sweet, heavy reek of roasted iron ore. Wat had set up a secondary crucible near the main forge—a high, narrow cylinder of refractory firebrick that Thomas had helped him line with a mixture of crushed quartz and river clay to withstand the intense heat of the deep coal.
The blacksmith was standing by the air pipe, his face completely black except for the white ring around his good eye. He was working a double-acting leather bellows with his right arm, his muscles bunching like oak knots with every stroke. The furnace didn't give off the lazy, orange glow of a standard hearth; it hissed with a terrifying, white-hot ferocity that turned the air above the rim into a shimmering lens of heat.
"She's cooking, Thomas," Wat shouted over the roar of the blast. "The slag is running like honey from the tap hole. It's got that blue skin on it you told me to look for."
Thomas stepped closer, shielding his face with his leather sleeve. This was the true core of his technology tree—not the steam engine or the mechanical looms, but the metallurgy that made them possible. If they could consistently smelt high-carbon crucible steel instead of the soft, slag-riddled wrought iron of the local smiths, they wouldn't just have better weapons; they would have the bearings, the drill bits, and the piston rings needed to scale up the power.
"Let's see the pour," Thomas said.
Wat signaled to his two eldest boys. Using long, iron-tonged bars that had been cooled in the water trough, they tipped the crucible. A stream of liquid metal, brilliant and white enough to leave a green ghost in Thomas's vision, spilled into a row of sand molds laid out on the dirt floor. The heat was instantaneous, scorching the hair on Thomas's forearms from five feet away.
As the metal settled into the shapes, it began to cool, shifting from white to a deep, angry cherry red, and finally to a dull, stony grey. The molds were shaped for short, heavy wedges—the blades for the new water-gate valves and the internal teeth for the engine's gear train.
Wat spat into the dust, his single eye tracking the cooling metal with a craftsman's suspicion. "It's different iron, Thomas. It doesn't spark like the Spanish bars we buy in Oakhaven. It looks... cold. Even when it's hot."
"It's steel, Wat," Thomas said, kneeling down to check the surface of a cooling wedge for gas bubbles. "The carbon is locked into the iron instead of being hammered out on the anvil. It's three times harder than the Baron's swords. If his knights hit a line of these pikes, their lances will split like straw."
Suddenly, the phone in his tunic let out a long, dual vibration—the specific cadence he had set for an incoming voice note.
Thomas stepped back into the shadow of the fuel shed, away from Wat and the boys. His hand was shaking slightly as he pulled the device from his wool. The screen showed a new file from 2026, the data packet appearing like a clean drop of water on a dusty sheet of parchment.
He pressed his thumb to the speaker and held the phone to his ear, blocking out the rhythmic shhh-hiss of the bellows.
"Tom? It's Sarah." Her voice was tiny, accompanied by the familiar, digital hiss of a hands-free car microphone. There was a weird, hollow delay in her words, as if she were speaking from the bottom of a well. "Mom told me you sent that message about the lighting project. I'm actually driving past the university library right now—the old one where we used to hide out during finals. They're tearing down the north wing to build that new computational lab you wanted to work at. It made me sad. It feels like everything we built is getting overwritten by something faster. I hope your site is going well. Don't forget to look up from the blueprints once in a while. Love you."
The message ended with a sharp, electronic click.
Thomas stood in the darkness of the shed, his boots resting on a pile of raw charcoal. He looked out through the slats at the forge yard—at Wat wiping his greasy brow with a rag, at the white-hot steel skin forming over the sand molds, at the little brick cottages rising by the river bend under a grey, 12th-century sky.
He wasn't overwriting his old world. He was writing a new one over the top of this one, a line of code at a time, using iron and clay for his syntax. But Sarah's voice remained exactly the same—the voice of a girl who was currently living in a future that his every action was slowly, silently unmaking.
"Thomas?" Wat called out from the furnace, his heavy wrench clanking against the brick rim. "The third mold is cool enough to crack. You want to see if the teeth are straight?"
Thomas tucked the phone back into his tunic, the warmth of the glass resting against his ribs like a small, battery-powered heart. He stepped back out into the white heat of the yard, his voice regaining its flat, engineering focus.
"Crack it," Thomas said. "We have twenty more to pour before the watchtower bell rings."