My body was a lie. In 2025, I thought I was in decent shape because I walked the length of a construction site twice a day and did forty minutes on a treadmill while watching news about the housing market. But forty minutes of cardio is not the same as spending sixteen hours dragging river stones up a muddy incline. I woke up on a pile of straw that felt like it was made of needles. Every muscle in my back was locked in a cramp so tight I couldn't even swear properly. My hands were the worst. The blisters from yesterday had popped, and the raw skin was stuck to the coarse fabric of my tunic.
I sat up and immediately wanted to throw up. The air was thick with the smell of the village, which I was starting to realize was a permanent feature of my new life. It was a mix of damp rot, unwashed bodies, and the charcoal smoke that was still clinging to my hair. I looked at my reflection in a bowl of stagnant water. My face was a mess of soot and pale skin. I looked like a ghost that had been dragged through a chimney.
Lao walked in, looking far too energetic for someone who had stayed up half the night. He dropped a wooden bowl of something that looked like gray paste on the floor next to me.
Eat it, he said. It's millet. It tastes like dirt, but it'll stop your heart from quitting.
I picked up the bowl. My fingers were shaking so hard the wooden spoon rattled against my teeth. The stuff tasted exactly how it looked. Bland, gritty, and vaguely earthy. In my old life, I would have complained if my latte was two degrees too cold. Now, I was shoveling gray sludge into my mouth like it was a five star meal.
We have a problem, Lao said, squatting down next to me. The elders are talking again. They saw the bricks you made, sure. But the water is still rising. They say we are wasting wood on fire when we should be building rafts. A few of the younger men are planning to leave for the high pass.
I swallowed a mouthful of the millet and felt it sit like a rock in my stomach. Let them leave, I said. If they want to freeze to death in the mountains, that is their business. But the moment they walk out that gate, they don't get to come back when the dam is finished.
The dam won't matter if we can't move the water, Lu, Lao reminded me. He was right, even if I hated hearing it from him. The bricks were just a start. A wall without a way to relieve the pressure is just a tombstone waiting to fall over.
I need iron, I said. I stood up, or tried to. My knees buckled, and I had to grab Lao's shoulder to keep from hitting the dirt. The big man didn't even flinch. He just held me up until my legs remembered how to work.
There's no iron here, Lao said. The Governor took all the metal for the wars in the North. We have a few broken plows and some rusted scrap, but that's it.
Then we go to the scrap, I said. I hobbled toward the door, feeling like an old man. We need to build a bloomery.
What's a bloomery?
It's a machine that turns garbage into tools, I told him.
The village was a mess. The rain had slowed to a light drizzle, but the humidity was nearly one hundred percent. The bricks we had fired yesterday were stacked near the breach, but the villagers were standing around them, looking lost. They were waiting for me to tell them what to do. It was a terrifying feeling. In my old life, I was responsible for budgets and safety codes. Here, I was responsible for their heartbeats.
I found a spot near the kilns where the ground was slightly firmer. I started sketching in the mud with a stick. I didn't have my drafting software. I didn't have a laser level. I had to use my eyes and a piece of string to get the proportions right. I needed a vertical furnace about six feet tall. It had to be lined with the same clay we used for the bricks, but thicker.
I spent the next four hours screaming at people. It was the only way to get them to understand the precision I needed. If the walls of the bloomery weren't straight, the heat wouldn't rise correctly. If the air holes were too small, the fire would choke. My voice was a rasping wreck by noon.
The work was brutal. We had to break up the rusted scrap iron into small pieces. I found an old, cracked cauldron and a couple of shattered plowshares. We smashed them with heavy river stones until my ears rang and my arms felt like they were on fire.
By the afternoon, the bloomery was standing. It looked like an ugly, bloated chimney made of red clay and stone. I had rigged up a crude bellows system using some cured pig skins and wooden planks. It was a far cry from the high pressure oxygen injectors I was used to, but it was all we had.
Light it, I told Lao.
The fire started slow. We fed it charcoal, which we had spent all morning making by half burning wood under a layer of dirt. The smoke was black and oily. I stood by the bellows, watching the air intake.
Pump it! I shouted at the two men on the planks. Faster! I need a steady rhythm!
The bellows went up and down. Squeak, puff. Squeak, puff. It was the heartbeat of the project. I watched the top of the furnace. For an hour, nothing happened. Then, the smoke began to change. It went from black to a deep, angry orange. The heat coming off the clay walls was intense. I could feel the hair on my arms singeing.
This was the part of the math that usually happened inside a computer. The chemical reduction of iron oxide. In 2025, it was a button press. Here, it was a battle against the elements. I kept feeding in charcoal and scrap iron, layer by layer. My eyes were stinging from the fumes, and my skin was covered in a layer of fine, gray ash.
Hours passed. The sun began to set, casting long, bloody shadows across the mud. The villagers gathered at a distance, watching the furnace roar. They were silent. Even the elders had stopped complaining. The sheer violence of the fire seemed to have stunned them.
I checked the tap hole at the bottom. The slag, the waste material, should have been liquid by now. I took a long wooden pole and poked at the seal. A stream of glowing, black liquid oozed out, hissing as it hit the wet ground.
Is that it? Lao asked, shielding his eyes. Is that the iron?
No, I said. That's the garbage. The iron stays inside. It's a bloom. A sponge of metal.
At least, that was the theory. I had never actually built one of these with my own hands. I had read the history books. I knew the chemistry. But knowing the melting point of iron is one thing; achieving it in a mud hut in the middle of a flood is another.
We kept the fire going until well past midnight. I was hallucinating from the heat and the exhaustion. I thought I heard the sound of a jackhammer in the distance. I thought I saw the glowing lights of a city on the horizon. But when I blinked, it was just the sparks flying into the dark sky.
Break it open, I finally ordered.
Lao and another man took heavy wooden mallets and smashed the front of the furnace. The clay walls shattered, spilling red hot coals everywhere. In the center of the mess sat a dark, glowing lump about the size of a man's head.
Is that it? Lao whispered.
I grabbed a pair of tongs and pulled the lump out. It was heavy. Much heavier than it looked. But as it cooled, my heart sank. It wasn't a solid piece of iron. It was a porous, brittle mess of metal and trapped slag. It looked like a piece of burnt toast made of rock.
I took a hammer and tapped it. A large chunk flaked off immediately.
It's garbage, I muttered. My voice was flat. All that work. All that wood. And all I had was a pile of slag.
The men at the bellows stopped pumping. They looked at the lump of cooling rock, then at me. I could feel the hope in the air dying. It was a heavy, cold feeling that was worse than the rain.
The elder stepped forward into the light of the dying coals. I told you, he said. You cannot force the earth to give up its secrets. You have angered the spirits of the mountain, and now we have nothing but ash.
I didn't answer him. I couldn't. I was too tired to argue, and too disappointed to care. I looked at my hands. They were black, bloody, and useless. I had failed. The 2025 genius had been beaten by a pile of dirt and some charcoal.
Go home, I said to the villagers. Go back to your huts.
I sat down in the mud next to the failed bloom. Lao stayed behind, standing like a shadow in the darkness.
What now? he asked.
I didn't know. I looked at the slag heap. My mind was trying to run the numbers again. What went wrong? Was the temperature too low? Was the charcoal poor quality? Was the air flow inconsistent? It was probably all of those things. I was trying to run a marathon before I could crawl.
I picked up a piece of the brittle iron. It snapped in my fingers. I wanted to cry, but I didn't have the energy for it. I just sat there, covered in filth, while the river continued to roar in the distance.
I am not a god, I thought. I am just a man who knows a few things. And those things don't mean anything if I can't make them work here.
Lao sat down next to me. He picked up a piece of the scrap. We can try again tomorrow, he said.
With what? I asked. We used half the scrap we had. We used three days' worth of charcoal. The people are hungry, Lao. They won't give me another day.
Then we don't ask them, Lao said. We just do it.
I looked at him. He was covered in soot just like I was. His eyes were bloodshot. But he wasn't giving up. He didn't have a 2025 education. He didn't have a blueprint. He just had a stubborn refusal to die in the mud.
I felt a spark of something move in my chest. It wasn't hope. It was spite. I was an architect. I had built skyscrapers in earthquakes zones. I had managed projects with thousands of variables. I wasn't going to let a 12th century furnace beat me.
The charcoal, I said. It was too wet. We need to kiln dry the wood properly before we turn it into coal. And the bellows... the rhythm was wrong. We need a steady pressure, not just bursts of air.
Lao nodded. I don't know what any of that means, but if you say so.
I stood up. My back felt like it was made of broken glass, but I didn't care. I looked at the slag heap. It wasn't a failure. It was a data point.
I grabbed the charcoal stick and the piece of silk from my pocket. It was crumpled and stained, but there was still a bit of white space left. I started to draw a new intake system. A better one. One that used a water wheel to drive the bellows.
Wait, I said, looking toward the river. We don't need men to pump the air. We have the river. The very thing that is trying to kill us is going to be the thing that saves us.
Lao looked at the water, then at me. You're going to use the river to blow the fire?
I am going to use the river to do everything, I said.
I looked at my ruined hands. They were shaking, but they were already starting to draw. I wasn't going to build a wall. I was going to build an engine.
The sun started to come up over the horizon, a pale, weak light that barely cut through the mist. The village was still under water. The people were still hungry. But the fire in the bloomery wasn't dead. There were still a few glowing embers in the ash.
I picked up a piece of the failed iron and threw it back into the pit.
We start again, I said.
Lao didn't argue. He just grabbed a shovel and started clearing the ash.
I looked at the blueprint in my head. It was growing. It was getting more complex. It was shifting from a simple wall to a system of gears and levers. I was going to turn this province into a factory if it was the last thing I did.
I walked toward the riverbank, my mind already calculating the torque of a wooden wheel. I didn't need a goat. I didn't need spirits. I just needed a way to harness the energy that was currently trying to wash me away.
One gear, I whispered. One gear at a time.
I spent the next hour walking the bank, looking for a spot where the current was strongest. My boots were soaked, and my feet were numb, but I didn't feel the cold anymore. I was an architect again. I was solving a problem.
The blueprint was clear now. I could see the whole thing laid out in the air in front of me. The wheel, the axle, the bellows. It was all there. I just had to build it.
I turned back toward the village, the mud splashing against my legs. I saw the villagers coming out of their huts, looking at me with weary, suspicious eyes.
Get back to work! I shouted. We have a wheel to build!
They didn't move at first. But then Lao stood up and roared at them. They started to move. Slowly, but they moved.
I walked back to the bloomery and started to clear the debris. I had a lot of work to do before the next flood hit. But for the first time since I woke up in this world, I didn't feel like a victim. I felt like the man who was going to change everything.
I picked up a stone and started to mark the ground. The first gear would be here. The axle there.
It was going to be a long, difficult road. But I had the math on my side. And in the end, math is the only thing that matters.
I looked at the slag heap one last time and smiled. It was the best teacher I ever had. Tomorrow, the iron would be pure. Tomorrow, we would have the heart of the machine.