He fell, just before Willow's spell trapped the demons' 10 feet tall leader, just before Buffy jumped from the roof and buried her blade deep inside the demon's neck, just before Spike could tell him 'I love you too'.
Giles said he died quickly, and that there was only a second of pain. Spike asked if he was in Heaven now. No one could answer for sure.
There was a public funeral for all the fallen heroes. A monument was built. Tall and shiny and new, filled with names. His was near the top.
Life went on.
Buffy asked him to stay with them, with what's left of the Scooby Gang. And for a short while, he did. But at the end, it was too much. There was too much missing, for all of them. So he left.
He went around the world, to all the places he promised his dead lover he'd take him to, once the battle was won. And at all the places, he planted an enchanted seedling. Once the tree was grown, his lover's name would be carved on the trunk.
After that, he went to LA, where Angel was still doing his demon-fighting business. He was alone now. Spike joined him for the next few decades. There was still a hole in his heart, but he was doing okay.
Life went on.
Almost a century after the final battle, Spike had a dream. He left for Cleveland.
He laughed at the irony that the boy was returned to him at another Hellmouth. The baby opened his eyes and smiled at him, waving his chubby little hand. Spike was happy.
The boy's name was Alex. This time around, he had two loving parents, and a vampire guardian angel.
When Alex was four, his kindergarten teacher told his parents that he had a very active imagination. Spike thought maybe he should tell the boy different bedtime stories from now on. He went to the bookshop and bought all the Disney storybooks.
Alex asked for a baby brother or sister for Christmas. His parents laughed and told him it will be here in a few months' time.
When his baby sister was born, his parents asked him to name her. He said, 'Willow'. Spike asked him why, but the boy simply shrugged and said it was a pretty name. Spike agreed.
They started learning about the war in middle school. Their History teacher told them stories of the war heroes. Alex put his hand up. Surely the one-eyed hero didn't hate all vampires, he said, if his lover was one. His teacher looked at him strangely, and asked how he knew. Alex shrugged.
Spike watched him turning back and forth in his sleep, mumbling names and places and latin. The boy had started to dream, and Spike had no idea what to do.
"Tell him," said Angel when he called.
On a long weekend, Spike took the boy to Sunnydale. Next to the crater, there were three graves. Alex traced the name on the oldest one. It said, "Xander Harris, 1980 – 2006, Beloved Friend, He Saved The World, A Lot."
"Why am I here?" he asked, but Spike did not answer. He knelt down in front of Xander Harris' gravestone, and he was crying. Alex put his arms around his vampire and comforted him until he calmed down. He knew why he was here.
They sat down on the grass. Spike rested against Xander's gravestone, and he started telling the boy everything.
The sun was almost up by the time he finished. The boy quietly asked where Willow was now. Spike told him to get in the car, and they drove away.
Willow, ancient even for a witch, broke down as soon as she saw the boy. He looked exactly like the best friend she had over a century ago. Alex went over to hug her without hestitation, as if he had done this a thousand times before.
She was lonely. Her wife had died a long time ago, and she had been in the nursing home for almost two decades. Her only visitor was Spike. Alex promised to come as often as possible.
Willow died shortly after her 140th birthday. Her last few years were happy, and she died in a warm bed with Spike and Alex around her. They buried her next to her friends.
Cleveland, as a Hellmouth, was much safer than Sunnydale had been, which was probably because there were about fifty slayers in town at all times. But even that didn't stop Alex being attacked by muggers on his way home from football practice one night. Spike found the boy lying in an alley, his head bloody and his skin pale from bloodloss and the cold. For a moment, Spike couldn't move. His head was filled with images of another boy, who died so long ago. But this boy here was alive. Spike could hear his breathing, and his heartbeat. He was very much alive.
The boy had a pretty bad concussion, but he was other-wisely fine.
Spike spent every night after that with the boy. He read and drew and thought, as the boy slept on. He just needed to hear him breathe, to know that he was there.
The boy changed after he turned eighteen. He used to ramble on and on – just like his boy did. But now he was quiet and he seemed to be avoiding Spike.
One night, as he looked up from his book, he found the boy staring at him.
"I think," the boy said, "I think I love you."
Spike did not know what to think. He jumped out of the window and ran.
He went to LA to find Angel, who called him a stupidhead and told him to go back.
Alex got home the next evening and found his vampire sitting cross-legged on his bed, a book in his hand. Spike looked at his boy and smiled.
"I love you too."