Seo charged through the monsters. Flipping across a Oxyshorn Demon's back, twisting the flip so that she could kick out at a flying Woxor Demon, nearby.

Xander spun around, shooting at the snarling noises that tore through the air.
As Willow blasted as many monsters as she could with magical energy.

They were making progress. Slow progress, but progress. Seo could see, in the distance, a town long-abandoned, looming empty in the night.

Sunnydale.

And one single building had power. Lights inside the windows. And more demons and monsters circling the outside than any other.

A huge, tall building, towering over all the others.

Seo managed to punch the nearest demons so that they dropped to the ground. Unconscious, but not dead. She didn't like killing things — not if she could help it.

"That building," said Seo, grabbing the back of Willow's wheelchair and pushing it towards the city of Sunnydale. "She built it specifically for this. Didn't she?"

"It wasn't there when Sunnydale was destroyed," Willow confirmed. "But why…?"

Seo knew why.

Knew exactly where the top floor of that building was located, and why it had needed to be that tall, and in that precise location.

"That's where the portal opens up," said Seo. "She's guarding it."

Buffy clutched her head, trying to stop a cry of pain from passing through her lips.
Elizabeth, on the other side of the bars, staggered. Her own hand to her head. "It's happening," she said, reaching out with her free hand to catch herself. Gave a little, breathless laugh. "I can feel it. See everything you've ever done."

And Buffy felt that burning, bitter hatred crawling through her. Felt a horrible sense of madness and fear and desperation blossoming inside herself, one she couldn't face and didn't want to admit even existed.

No!

She was herself!

She had to… had to be… it wasn't her fault…!

"You can't win," Buffy said. "I'm… I've got a plan. A plan… to use your family against you. Escape…"

Then she doubled over.

Gritting her teeth, howling in anger and fury and frustration.

"No, I'm not Elizabeth, I'm Buffy!" she shouted. "Buffy! Buffy! Buffy!"

"And so am I!" shouted Elizabeth, equally breathless and unstable. "We're the same! We're going to be the same!"

"It's what the Crystallizer's doing to us," Buffy breathed.

Because she knew. Because she could see the whole plan weaving together inside her mind, along with the memory of seven long years, locked up in a UNIT prison. And the time after she escaped…

Releasing Abaddon.

Punching holes in the universe, to invite the monsters to Sunnydale.

"You said you liked being you!" shouted Buffy, through the pain and confusion. Or… she thought she was Buffy. How could she tell? "Why with the personality squashing? Why with the making-us-each-other?"

Elizabeth gave a small laugh. "You really don't get it, yet?" she said. Shrugged out of her lab coat, to reveal her clothing.

The exact same that Buffy was wearing.

And Buffy had a horrible feeling, deep down inside, that she knew exactly what Elizabeth was planning. Why Elizabeth had changed them both into the same clothes. Why Elizabeth had needed to wait for the Crystallizer to crank into full action before Seo showed up.

Elizabeth pointed to the cell next to Buffy. The one identical in every way. "We're the same," she said. "Exactly the same. When your daughter shows up to rescue you… she won't know which one's her mom. And which is the imposter."

"She'll know," Buffy said.

"How?" Elizabeth gestured between them. "We look the same. We're gaining each other's memories. Anything different about us… is equalizing… under the Crystallizer." She staggered towards the cell beside Buffy. "Your stupid daughter… will save me. Thinking it's you."

"You're underestimating her," said Buffy. Grabbing the bars, forcing herself to remember… she was Buffy. She was herself. She wasn't Elizabeth. "Seo's clever. Like her father."

Elizabeth stumbled onto the floor. Her hands around her head. Forcing herself forwards, despite the pain. Forcing herself to seem calm, collected, controlled…

Even as time was resculpting both of them.

"I'm gaining freedom, along with both a husband and a child," said Elizabeth, grinning. "I'm going to like usurping your life, other-me. I'm really looking forwards to it."

"A husband?" said Buffy.

Then, suddenly, burst out laughing.

As she realized…

"You haven't gotten that memory, yet!" Buffy cried. "Oh, this is great! You know all about my life, but you don't know who Seo's father is! You have absolutely no idea where she came from."

Elizabeth didn't answer.

"Come on, you know there's something weird about her!" said Buffy. "She's the Key. And she's my daughter, even though she looks almost the same age as me."

The beats in her head were intensifying. Trying to drown out any and all thought inside her.

But Buffy didn't let them.

"Dig around in my memories!" shouted Buffy. "Figure it out! Find out whose life you're trying to usurp, who I love, and if you'd really like that as much as you think!"

Elizabeth froze.

Her face suddenly going pale.

As she stared at Buffy in wide-eyed horror. "No…"

Buffy cracked up. "There you go! That's the right memory!"

"You!" screamed Elizabeth, dragging herself to her feet. "She's… her father is…!"

"Your life is hatred and grudges," said Buffy, "mine is love and forgiveness. That's what separates us, Elizabeth! It's how Seo will know, the moment she sees us, who's who. No matter how long we've spent around the Crystallizer!"

Elizabeth's whole body was shaking.

Her eyes murderous.

"I'm going to kill you!" Elizabeth screamed, wrenching an iron bar off the front of the cell, and running at Buffy. "I'll kill you for that!"

The bar clanged against those keeping Buffy trapped inside her own cell.

Buffy laughed, even harder. "I don't just admire him," she said. "I love him! I trust him — with everything I've got in me! And I love Seo — not just because she's mine. But because she's his!"

The statement got the desired reaction from Elizabeth.

As Elizabeth unlocked Buffy's cell, slamming the bars aside and racing inside. Swinging the iron bar at Buffy, hard as she could.

Buffy caught it before it struck, then shoved the bar back up, throwing Elizabeth with it — over her shoulder and crashing into the far wall.

"You yanked that bar off," said Buffy, springing to her feet. "That means you're getting my Slayer strength… and so am I. The Crystallizer's neutralized the drugs."

Elizabeth also jumped back to her feet, throwing a flip kick that shoved Buffy away from the door. "I gained your strength," said Elizabeth. "And all your knowledge about fighting."

She punched out, and Buffy blocked her. Then kicked, trying to off-balance her, race outside to help her daughter, but Elizabeth caught the leg and twisted it around, shoving Buffy so she flew through the air.

The Crystallizer pulsed, and they both cried out, at once.

Each one's injuries and scrapes imprinting onto the other, as the Crystallizer did its work. Morphing and merging them together.

"I won't let you hurt my daughter!" shouted Elizabeth.

"You're not going to escape!" said Buffy. "I won't let you. This is my plan, and I've…" Then realized, "No! Wait! That's wrong. I'm the Buffy-one. You're the Elizabeth-one."

The Crystallizer was working.

Just the way that Elizabeth had said it would. Working and whirring and changing around…

Which was when Buffy realized something. Something Elizabeth hadn't thought of. Something that chilled her to the bone.

"The Crystallizer only does this," Buffy breathed, "when the Time Lords are up to something. Manipulating the outcomes."

Elizabeth lunged at Buffy, fury written across her every feature. "Monster!" she screamed, grabbing the bar and trying to slam it down across Buffy's head. "Murderer! Insane nutcase!"

Buffy only just managed to flip out of the way in time. "I'm not in control!" Buffy screamed. "I mean… you're not in control! Whatever! My point is, the Crystallizer's manipulating something else, and we're just getting the side-effects!"

Elizabeth charged again, and Buffy caught her by the arm.

"Someone wants a portal open to this Time War reality, you idiot!" shouted Buffy, in her face. "Someone besides us! Someone who's happy to destroy the world as long as it lets them get free! What the hell are we doing, giving it to them? We have to work together! Stop this!"

Elizabeth paused.

Breathing hard.

"Work together," she said. Her eyes darting over to the Crystallizer. Then she stepped away from Buffy. "Yes! Yes, you're right. We've got to save the world." Raced over to the lab table, gesturing for Buffy to follow. She picked up the Crystallizer. Tossed it to Buffy. "Hold that. I know something that can get rid of it."

Buffy grinned, a little.

"Guess a little injection of Buffy into your brain is good for you, after all, huh?" she said. The Crystallizer was definitely working overtime on something. Question was… what? And why?

"And a little of my cleverness in you would be good, too," Elizabeth agreed. Her voice darkening, as she came back. "If you had it."

Buffy looked up, just too late to stop Elizabeth from slamming an iron bar into her head.
Buffy slumped, her world fading to black.

The Crystallizer sliding from her hands.

"Imbecile," said Elizabeth.