Twelve years later — Oxford, 2011

"Hello, Oz!" Seo cried, chirpily, her hands behind her back, bouncing on her feet. "Can you hear me?"

Oz didn't respond. He just kept staring straight ahead, blankly.

"Yoo-hoo!" Seo said. She waved in front of him, snapped her fingers, did some jumping jacks. "Oz! Come on, I know it's you. Easy to spot — the one person who'd make an absolutely rubbish cyberman." She grinned at him. "You remember me, right? We met during that thing with Father and Jenny and Riley Finn. Can't have been that long ago."

Still, nothing.

Alison analyzed him, carefully. "Who is this? And… why would he make a bad cyberman?" She cringed. "Or do I not want to ask?"

Seo glanced over her shoulder. "What? Oh, that! Well, he's a werewolf. Not good cyberman material." She leaned her head to the side. "Unless I could make a cyber-werewolf. I wonder…"

Alison cleared her throat, pointedly.

Seo blinked, and snapped back to herself, as she noticed Oz slumping in place. She reached out, trying to prop him back up. "You know, it's funny," she said, "but he looks quite a bit younger than the last time I saw him."

Another figure suddenly appeared before them. This one also looked young, like a teenager, her hair red and her eyes vacant. And — oddest thing, yet — Alison knew her!

The zombie almost fell over.

Alison raced out and caught her.

"But she's… but it can't be!" Alison cried. She managed to get the girl steady on her feet — although still zombified. "It's the magic one from the Slayer Institute! Willow… something!"

Seo left Oz and rushed over to Willow.

"Willow," Seo breathed. She felt for a pulse. Looked into her pupils. Tried to work out anything that could be causing the trance. "No, no, no. This can't be…!"

Seo froze, for a second. Her hands were shaking.

She stepped back.

"This is wrong," Seo said. She looked around herself, and shuddered. "All wrong. This is her when she's just a kid! Everything with the First, the Toclafane, the Demon Civil War — none of it's happened to her, yet!"

"So there's something wrong with time?" Alison asked.

Seo spun around. "Time? Not just time! Something's wrong with all of causality, Alison! Don't you see?" She pointed at Willow. "Without Willow, Mom would be dead! Several times over! If it weren't for Willow, you would be dead! But you're not, so…!"

Seo stopped, in mid-sentence. Froze. "Unless…" Her entire expression grew panicked, as the possibility crashed on top of her.

"What?" Alison asked. "What is it?"

"Unless… we didn't land the TARDIS in Oxford," Seo said, "but in Sunnydale, back in Mom's past — and time hasn't had a chance to catch up yet."

Alison grimaced. She suddenly felt very mortal. "You mean… I'm going to die?"

Seo grabbed Alison by the hand, tightly. "No. But we have to find Mom — and soon." She ran back to the main street, where more of those lizards were skittering around. "You're right — everything happening in Oxford right now is linked to Mom's childhood. She's the key to all of this. And I'm betting that whatever happened in Mom's past, in Sunnydale, will explain precisely what happened to Father."

Made sense to Alison. Well, sort of.

"I don't know where your mum went, though," Alison insisted. "She said something about the Doctor, and that she couldn't keep control, anymore. And then she was off!"

Seo's eyes were fixed on those silver lizards — still scuttling, en masse, to some unknown destination. "Follow the trouble," she muttered, "and you'll find my parents."

She yanked Alison after her, as she sprinted down the street, following the lizards. If she was right — and there was always a chance that she wasn't — there was some sort of barrier or doorway or time corridor, linking this place to Sunnydale.

And if they didn't find it soon… Willow's extraction from history would catch up with them… and Alison would be dead.