The engine coughed. A wet, metallic sound. Like a throat clearing.

"I told you," I said. My voice was flat. Dry. "It’s the gasket. Again."

Thomas did not look up. He was wiping his hands on a rag. The rag was red. Not with blood. With oil. Thick, black oil. It stained his knuckles. It stained his eyes. He looked tired. We all looked tired.

"Fix it," he said.

"I am fixing it."

"Fix it faster."

The air in the bunker was thick. It tasted of rust. And fear. And the sour sweat of men who had not slept in days. The walls were concrete. Cold. Close. We were in a box. A small, dark box under the city. The city above was burning. I could feel the heat. It seeped through the floor. It vibrated in my teeth.

I am not a man. I will tell you that now. I am a thing made of smoke and iron. A spirit bound to the machine. I have no name. They call me the Keeper. I live in the turbine. I breathe the steam. I am the heartbeat of this place. And I am dying.

My heart is a piston. It is cracked. A hairline fracture. It runs through the center. It is spreading. With every beat, the crack widens. I feel the cold air inside me. It is sweet. It is wrong.

Thomas is my ally. Or he thinks he is. He is a good man. He has kind eyes. He gives me the best oil. He speaks to me as if I were a dog. Or a child. He does not know what I am. He thinks I am a machine. A complex, temperamental machine.

"Stop complaining," he said. He pulled a wrench from his belt. It was heavy. Steel. Cold. "The shelling is coming back. We need power. For the lights. For the radio."

"The radio is broken," I said.

"The radio is important. We have to send the signal. To the others. To the world."

"To tell them what?"

"That we are here. That we are holding the line. That the fire is contained."

It was a lie. A small, necessary lie. The fire was not contained. It was spreading. The city was ash. The people were gone. Or dead. There was no difference.

I worked. My hands moved. They were not hands. They were extensions of the turbine. They moved with the rhythm of the gears. Click. Clank. Click. Clank. I tightened the bolt. The crack in my heart pulsed. A sharp pain. I ignored it. I am good at ignoring pain. It is my nature.

Outside, the sky turned white. Then red. The ground shook. A deep, resonant boom. The dust fell from the ceiling. It settled on Thomas’s face. He did not brush it off.

"Another one," he whispered.

"Yes."

"Is it close?"

"Yes."

He sat down on the floor. He leaned against the wall. The concrete was damp. He looked at me. His eyes were hollow.

"Can you do it?" he asked. "Can you keep it running?"

"I will try."

"Try is not enough. We need to survive. We need to be seen. We need justice."

The word hung in the air. Justice. A strange word. For who? For the dead? For the living? For me?

I looked at the turbine. It was beautiful. In a terrible way. The metal was polished. The gears were perfect. It was a masterpiece of industry. And it was a cage. My cage.

I thought of the seed. I had it. In my pocket. A small, green thing. A plant. I had found it in the rubble before the doors closed. A weed. A stubborn, green weed. I had potted it. I had watered it with my own breath. I had kept it alive. It was the only living thing here. Besides Thomas. And me.

I reached into my pocket. I touched the pot. It was warm. The plant was growing. Slowly. But it was growing. It was pushing through the soil. It was reaching for light. There was no light. Only the glow of the furnace.

"Thomas," I said.

He looked up.

"What?"

"The plant."

"What about it?"

"It is dying."

He frowned. "Why?"

"The soil is too hot. The air is too dry. It needs water. Clean water. Not steam. Not oil. Water."

He laughed. A short, sharp bark. "We have no clean water. We have engine coolant. We have sewage. We have nothing."

"Then it will die."

"It is a weed. It does not matter."

"It matters to me."

He stood up. He walked to the corner. He picked up a can. He poured a small amount of liquid into a cup. It was clear. It was cold. It was the last of the distilled water. The water we used for the medical kits. The water that could save a life.

He held it out to me.

"Drink," he said.

"I do not drink. I need it for the plant."

His face changed. The kindness vanished. The anger rose. It was cold. It was hard.

"You are being selfish," he said.

"I am not. The plant is part of me. If it dies, I die."

"I am dying too!" he shouted. His voice echoed in the small space. The dust fell again. "We are all dying! And you care about a weed? You care about a feeling?"

"It is more than a feeling. It is life. Real life. Not metal. Not smoke. Life."

He threw the cup at me. It shattered. The water splashed on the floor. It soaked into the cracks. The plant in my pocket wilted. I felt it. A sudden, sharp pain in my chest. The crack widened.

I looked at him. I did not speak. I did not need to. He saw the pain. He saw the crack in my eyes. It glowed. A faint, blue light.

He stopped. He looked at me. Really looked.

"What are you?" he whispered.

I did not answer. I could not. The words were stuck in my throat. The metal in my throat was tight.

"I am..." I started.

"Are you human?"

"No."

"Then what?"

"I am the engine. I am the heart. I am the ghost."

He backed away. His hand went to his belt. To the wrench. Or the gun. I did not know which. He looked at me with fear. And pity. And something else. Recognition.

"I don't understand," he said.

"You don't have to."

"Then why?"

"Why what?"

"Why do you stay? Why do you work? Why do you care about the plant? Why do you care about me?"

I looked at the turbine. It was spinning. Fast. Too fast. The noise was a scream.

"Because I am holding it together," I said. "With my life. With my pain. If I stop, it explodes. If it explodes, the city burns. All of it. The ruins. The dead. The memory."

"That is not justice," he said.

"No. It is duty."

He sat down. He put his head in his hands. His shoulders shook. I could not tell if he was crying or trembling.

"I am tired," he said.

"I know."

"I want to go home."

"Home is gone."

"I know. I just want to stop."

I looked at the plant. It was brown. It was dry. It was dead. The crack in my heart was wide. I could feel the air rushing in. It was freezing.

I knew what I had to do.

I walked to the control panel. My steps were slow. Heavy. The metal in my legs was brittle. I placed my hand on the main lever. It was cold. It was smooth.

"Thomas," I said.

He looked up. His eyes were clear.

"I am going to open the valve," I said.

His face went pale. "No. Don't. The pressure. It will blow the walls."

"I know."

"Then we die."

"Yes."

"Why?"

"Because the city is gone. Because the fire is winning. Because there is no one to save. And because I am tired."

He stood up. He walked to me. He put his hand on my arm. His hand was warm. It was the last warmth I would ever feel.

"You are not a machine," he said. "You are a person."

"I am a ghost."

"No. You are my friend."

I smiled. It was a small, sad smile.

"Goodbye, Thomas."

"Goodbye."

I pulled the lever.

The sound was deafening. A roar. A howl. The air turned white. The light was blinding. I felt the crack in my heart shatter. The pieces flew out. They were small. They were sharp. They were beautiful.

I felt the plant. In my pocket. It burst into bloom. A sudden, violent burst of green. It was not a weed. It was a flower. A blue flower. It grew through the fabric. It grew through my hand. It wrapped around my arm.

I felt it. The life. The green. The coolness.

The walls cracked. The concrete fell. The sky opened up. It was night. The stars were out. They were bright. They were cold.

I did not die. I did not explode. I changed.

The metal in my body turned to dust. The smoke turned to mist. The pain vanished.

I was gone.

And the flower remained.

It stood in the rubble. In the dark. In the cold.

It was alive.

It was the only thing alive.

And it was beautiful.

The end.