The bus smelled of wet wool and diesel. I counted the stops. One. Two. My brother, Elias, sat across from me. He was shivering. Not from cold. From the hum.

I looked at his hand. His finger. The left index. It was gone. Not cut. Just... absent. A smooth stump where the bone should have been.

"Did you count?" I asked. My voice was flat. Professional. We were engineers. We dealt in loads and stresses.

Elias nodded. He didn't look at me. He looked at the window. The rain blurred the town of Oakhaven into a grey smear.

"Three," he whispered.

"Four," I said.

We were back. We had come to retrieve the sample. The core. The thing in the basement of the old mill.

The bus stopped at the corner of Mill Street and 4th. We got off. The air was thick. It tasted of iron.

"Walk fast," Elias said.

We walked. Our shoes slapped the wet pavement. The town was quiet. No cars. No people. Just the rain.

The mill was at the end of the street. The doors were open. Black smoke curled out. It didn't rise. It hung there, like a cloud trapped in a jar.

We went inside. The floor was concrete. It was cold. It bit through my boots.

"Down," Elias said.

He pointed to a hatch. It was rusted. We pulled it up. It groaned. Metal on metal.

We climbed down the ladder. It was dark. My flashlight beam cut a cone through the dust.

The basement was a room. Stone walls. A single table in the center. On the table was a box.

It was lead. Heavy. It had no handle.

"Open it," Elias said.

I knelt. My knees hurt. I was thirty-four. My knees hurt now. I used to be twenty. I used to think time was a line. Now I knew it was a loop. Or a trap.

I lifted the lid.

The light from inside was white. It was not light. It was sound. I felt it in my teeth. In my spine.

It was a finger.

A human finger. Left index. It was perfect. It was warm. It twitched.

Elias stared at it. His face was pale.

"That's mine," he said.

I looked at his hand. The stump. I looked at the box. The finger.

"Take it," I said.

"I can't."

"Why?"

"Because I know what it does."

I stood up. My back cracked. "You know what?"

"It shows you the end."

I looked at the finger. It pulsed. A soft, red beat.

"I don't care about the end," I said. "I care about the solution. The stress fracture in the bridge. We need the data. The sample."

"The sample is the cost," Elias said. "That's the trade. You give it a part of you. It gives you the answer."

I laughed. It was a dry sound. "We are not children playing shop."

"I am a child," Elias said. His voice was small. "I have always been a child. And you are the older brother. You have to protect me."

I felt a surge of anger. It was hot. It burned in my chest. "I am protecting the town. The bridge is going to fail. Three hundred people. They will die in the water. Cold and dark. I will not let that happen."

"You don't understand," Elias said. "The knowledge is the curse. Knowing the future is a burden. It breaks you."

"I can carry it."

"Can you?"

I looked at the finger. It was so real. So warm. It felt like life.

"Give it to me," I said.

Elias shook his head. "You have to take it from the box. You have to claim it."

I reached into the box. My hand hovered over the finger. The air was static. My hair stood on end.

I grasped the finger.

It was heavy. Denser than bone. Denser than lead.

I pulled it out.

The light flared. It blinded me. I dropped the finger. It hit the table. *Clack.*

The light died.

The room was dark again.

I looked at my hand.

My left index finger was gone.

I screamed. It was a raw sound. It tore from my throat. I fell to my knees. I held my hand. I pressed against the stump. There was no blood. Just a cold, smooth void.

Elias was standing over me. He was holding the box.

"Look," he said.

He opened the box.

Inside was a finger.

It was mine.

The left index. The one I had just lost.

I looked at my hand. The stump.

I looked at the box. The finger.

"Swap it," Elias said. "Put yours in. Take the data out."

"What data?"

He pointed to the wall. There was a chalkboard. It had been there before. I hadn't seen it.

On the board was a calculation. A structural analysis. It was perfect. Every variable accounted for. The load distribution. The shear stress. The failure point.

It was the answer.

I looked at the finger in the box. It was warm. It was mine.

I looked at my empty hand.

"I don't want it," I said.

"You have to," Elias said. "The bridge."

I stood up. My legs were shaky. I walked to the table. I picked up the finger from the box. It was light. It was dead.

I put it on the table.

"Take it," I said to Elias. "You are the one who knows. You are the one who sees."

Elias frowned. "It is your hand."

"Your knowledge is the cost," I said. "I am the brother. I pay the price."

I picked up my own finger from the table. The one I had lost. It was fresh. It was real.

I put it in the box.

I closed the lid.

The light flared again.

I fell.

When I woke up, I was on the floor.

Elias was gone.

The box was empty.

I stood up. I looked at my hand.

The finger was there.

It was whole.

I walked up the ladder. I climbed out of the basement.

The mill was dark. The smoke had cleared.

I walked out into the street.

The rain had stopped. The sky was clear. It was starry.

I looked at my hand. I flexed the finger. It worked. It was mine.

I walked to the corner. The bus was there. It was waiting.

The doors opened. I got on.

I sat down. I looked at my hand.

I was whole.

The bus started. It pulled away from the curb.

I looked out the window. The town of Oakhaven slipped away.

I felt a weight in my chest. It was heavy. It was cold.

I knew the answer. I had seen it on the chalkboard. I knew when the bridge would fail. I knew how to stop it.

But I didn't remember how I had gotten the answer.

I didn't remember the box.

I didn't remember Elias.

I looked at my hand. The finger. It was warm.

It twitched.

I closed my eyes.

The bus moved forward.

I was alone.

I was whole.

And I was empty.