Disclaimers:

These are obviously not my characters, I'm just borrowing them from Joss Whedon and anyone else who owns them. Any dialogue from the series also belongs to him.

Spike took a swig of whiskey directly from the bottle. Lately he had been drinking himself silly every morning before passing out. He did this because it kept the dream at bay. The dream was the same every time – Dawn standing tied up on the ledge, he the only one who could stop the Doc from cutting her to open the portal. Only in the dream, he did what he had promised Buffy he would do – he saved Dawn, he saved the world, he saved Buffy. In a way the dream was nice, but then he would always wake up, and remember that in reality he hadn't saved Dawn. He'd been pushed off the ledge like a child.

He didn't know what was different about this day, except that he knew he had to stop the cycle. The only way he knew of to do that was to make the dream a reality. So the next night, when he woke up, he headed to Willy's Bar.

"Look, you little pipsqueak, I know you got connections, so just make it easy on yourself and tell me who I need to see."
Willy cringed. "Just because Buffy used to push me around doesn't mean-"
He was cut off by a savage uppercut from the vampire.
"Okay, okay! Big magic, huh? Black magic?"
Spike glared at him. "And what do you think, I want to use magic to pull a bloody rabbit out of a hat? I'm EVIL!"
"All right, all right. There's a house on Myers Ave – all the way at the end, tucked up in the trees. There's a man there who might be able to help you." Willy admitted.
"You got a name to go with that pathetic information?" Spike growled.
"From what I've heard, you won't need one."

Spike looked around. It was hard to tell if he'd gone back in time, as he was still in his crypt, where he'd performed the spell. Still, little details had changed – the position of the TV, the little things lying around. Only one way to know for sure, so he headed outside. He knew exactly where he would be – with the Scoobies, following Willow's bird to the tower. He'd chosen the time precisely. So he took another route to the tower. He watched from behind a nearby building as the group approached. Luckily his other self was at the back of the group. He reached out and pulled him into the alley, clapping his hand over his mouth to quiet him.

The other Spike's eyes went wide when he saw who'd pulled him in.

"Look, I gotta make this quick or they'll miss you. You're going to go up to the top of the tower to save the li'l bit. The Doc, from the spell to bring back Buffy's mum, he'll be there. You have to knock him off the tower. Don't underestimate him."
"What the hell?"
"There's no time to convince you. I came back from the future to fix this. Don't mess it up. If you do, you'll regret it. Trust me. Don't try to kill him, just knock him off as quickly as you can. If you fall off before you stop him, she'll die."
He shoved his earlier self back out of the alley. He'd done all he could. He just had to hope that he could do it.

Spike hurried into the makeshift building after his friends. He wasn't sure what to think about the strange visitor he'd just had. But after being this long undead and on the hellmouth he knew better than to ignore something like that. Buffy and the god were fighting, and the other Scoobies, except the witches, were fighting the minions. He joined the fight.

Soon enough Glory broke the Buffy-bot that she was actually fighting with, and the real Buffy appeared and started fighting her. Spike heard the kid scream from the top of the tower. That was exactly where the other Spike had said she'd be. And he'd said that creepy magic man was going to be up there. He heard noises.
"There's someone up there."
"What?"
"Up there, with Dawn." He said to Xander. Willow, hiding on the other side of the fight, must have heard him, or the noises, because he heard her voice in his head.
"Spike. Can you hear me?"
It startled him, but he spoke his answer aloud. "Yeah, loud and clear."
"Is there someone up there with Dawn?"
"Yeah, can't tell who." Though he had an idea.
"Get up there. Go now."
There was still a group of minions and crazy people between him and the stairs. He looked at it uncertainly.
"Yeah, but.."
"Go!" the witch yelled in his head. He saw her grab her honey's hand and suddenly the group was split down the middle, leaving him a place to run. He did so quickly, asking no more questions of the powerful redhead.

Spike reached the top of the crazy tower, finding the Doc standing between him and Dawn with a knife in his hand.
"Doesn't a fellow stay dead when you kill him?"
"Look who's talking."
"Come on, Doc, Let's you and me have a go."
His visitor had said to knock him off, not to try to kill him. Spike tried to keep that in mind as he traded blows with the Doc. He managed to knock the knife out of his hand, and it skittered across the metal grate and fell to the ground. Dawn screamed.
"Don't you worry, Li'l Bit. I'm gonna get you out of here."
The distraction almost lost him the fight, as the creepy man stuck his lizard-like tongue out and lashed the vampire with it. But that just made him mad, and he kicked up with a vicious blow to his groin, and the Doc fell to his knees.
Spike finished him off by swiping his other leg around and knocking him off the tower.
Dawn started crying. He stepped carefully over to her. "Don't cry, it's going to be okay now, see? Time's up, and you're not bleeding."

From his position across the street, the other Spike smiled as he faded out of existence, the world he came from being eradicated.

That's all for now. I'm working on a sequel, sort of a rewrite of S6, but it'll probably be a while. Check out my other stories if you like stories fixing Josh's mistakes!