The All Spark burned cold in Sam Witwicky's hands, smaller now, no bigger than a stop sign torn from its post. Around him Mission City was a graveyard of fire. Optimus Prime lay pinned beneath the rubble of a collapsed building, one great hand reaching toward the boy, the other crushed under steel.
"Sam," Optimus said, his voice a low engine of pain. "Push the Cube into my chest. Sacrifice me. The future of both our races depends on it."
Megatron was coming. Sam could hear him, the shriek of metal on asphalt, the laughter that was less a sound than a vibration in the teeth. Tanks of him. A whole war wearing one body.
But the Cube was talking.
Not in words. In pictures, in pressure, in a heat that climbed Sam's arms and pooled behind his eyes. He saw Cybertron, not as a ruin but as it had been: oceans of mercury, cities of light, a planet that sang. He saw the All Spark not as a weapon but as a mother, and he understood, suddenly and completely, that it had never wanted to be a bomb. It had been made to give life, and for millions of years it had been thrown across the stars like a grenade with the pin pulled.
"Sam!" Optimus roared.
Megatron crested the rubble, fusion cannon glowing. "Give me the All Spark, boy, and you may yet live as my pet."
Sam looked at the Cube. He looked at the great silver monster. And he did the one thing no one in this war had thought to do in a hundred lifetimes.
He held the Cube out toward Megatron and said, "You want it? Then take it. But it's awake now. And it remembers what you used to be."
The All Spark flared.
Megatron lunged, and his claws closed around the Cube, and Sam did not let go. The light went through both of them. Sam screamed. Somewhere far away he felt Mikaela's hands grabbing his belt, trying to pull him back, and he shouted at her to run, and she didn't, because she was Mikaela.
Inside the light, Sam was not in Mission City anymore.
He was standing in a hall of silver pillars, and across from him stood a Cybertronian he didn't recognize, smaller than Megatron, sleeker, his armor unscarred. The optics were the same furious red, but younger. Curious.
"This is what you were," Sam said. He didn't know how he knew. The Cube was speaking through him now, using his mouth, his fear, his stubborn human refusal to watch one more thing die. "Before the war. Before the Fallen put his hand on your spark and called it destiny. You were a builder."
The young Megatron stared at him. "I was a king."
"You were a brother." The image shifted. Optimus stood in the hall now, except he was not Optimus, he was Orion, and the two of them were laughing about something, two friends in a city that had not yet learned to burn.
"Lies," Megatron said, but his voice cracked on it.
"The All Spark made you," Sam said. "It made all of you. It's the only thing in this whole war that loved every single one of you the same. And you've spent four million years trying to swallow your own mother."
The light tightened. Sam felt it pulling at the seam of him, and he understood the choice the Cube was offering. It could not be a bomb again. It would not. But it could be a key. It could pour everything it was into one spark and either heal it or burn it hollow, and it did not have the wisdom to know which. It was old, but it was not human. It did not understand forgiveness. It needed a hand to guide it.
It needed Sam to choose.
He thought about his dad's glasses. He thought about the long absurd road that had dropped a kid from Tranquility into the middle of a god's family quarrel. He thought, ridiculously, of Bumblebee playing love songs through a busted radio because he couldn't say the words himself.
Kindness, Sam thought. Even now. Especially now.
"I'm not going to kill you," Sam told the monster. "I'm going to give you back."
He shoved the All Spark not into Megatron's chest but into his own, and then through himself, like threading a needle, and out the other side into the spark of the thing that had once been a builder and a brother and a king. He gave it everything. He gave it the memory of mercy that Megatron had cut out of himself a million years ago. He gave it Orion's laugh. He gave it the simple human idea, so small it was almost stupid, that you could put a weapon down.
Then the hall of pillars shattered, and Sam was on his back on the cracked asphalt of Mission City, and the All Spark was gone.
Not destroyed. Gone. Spent. Emptied into the world like water poured into sand.
Megatron knelt above him.
The great silver hand hung in the air, claws spread, and Sam stared up into the red optics and waited to die. Mikaela's grip was still on his belt. The fires crackled. Somewhere a siren wailed and gave up.
Megatron's hand trembled.
"What," Megatron said, "have you done to me."
It was not a roar. It was the smallest voice Sam had ever heard come out of something that size. The fusion cannon, half raised, sputtered and went dark. Megatron looked at his own claws as if they belonged to a stranger. Behind his optics something was moving, four million years of buried things clawing their way to the surface all at once, and the weight of it bent him.
"Megatron." Optimus had dragged himself free of the rubble, energon weeping from a dozen wounds, and he stood now with one shoulder lower than the other, beholding his brother. He did not raise a weapon. "You feel it."
"Get out of my processor," Megatron snarled, but he did not move, because the thing he was fighting was not outside him.
"It is not in your processor," Optimus said gently. "It never was. It is in your spark. It always was. You only forgot."
Sam lay between two titans and understood that he was watching something older than the human species try to remember how to be itself.
For a long moment nothing in Mission City moved.
Then Megatron rose. He turned from Sam, from Optimus, from the broken city, and he looked up at the smoke-gray sky as if searching it for a planet that no longer existed. When he spoke again his voice had changed. The cruelty hadn't vanished, Sam could still hear it, an old habit pressed into the metal, but under it was something raw and stunned and almost afraid.
"The Fallen will come for what I have failed to do," Megatron said. "He will not forgive this."
"Then you will not face him alone," said Optimus.
Megatron laughed, low and terrible and uncertain, and the sound was not quite the laugh from before. "Brothers again, Prime? After everything?"
"After everything," Optimus said. "That is the only time the word means anything."
Megatron looked down at Sam one last time, this small soft creature who had reached into a war god and handed him back his own buried heart.
"You should have run, boy," he said.
Sam picked himself up off the asphalt, every bone aching, his dad's glasses still somehow in his pocket. He met those red optics without flinching.
"Yeah," he said. "Everybody keeps telling me that."
Above them the smoke began, very slowly, to thin.