"I'm ready," Buffy told the Havchornom. She turned to them all. "Whatever you can do to allow me save her… just do it!"

The Havchornom all grinned, wickedly.

And — in a flash — Buffy found herself being transported to… somewhere else. An enclosed room with white walls, a white ceiling, and a white floor. She frowned, but then the walls and floor and ceiling began to change, the image she'd been seeing now superimposed on top of it, like a living hologram.

Except… Buffy realized… she could touch this one.

As she ran, the landscape around her shifted in the direction of her running. Like some complex simulated reality. Buffy hurled herself at the Yixolpot, just as it reached out for Seo again.

Flipped through the air, pulling out a concealed dagger she'd kept on her since arriving in the area outside the Tartarus Gate.

She missed landing on its head, but instead grabbed the fur on its back, using it to catch herself and yank herself back onto the monster's body.

Then plunged in her knife — a warning.

The Doctor saw monster narrowing in on Seo. Curious that it should always go for Seo, specifically… even when it had Jack in its jaws, it still discarded him in order to go after her.

"Maybe it's sentient," the Doctor proposed. Brain whirring, fast. "Or well trained. Could be someone knew she'd be here, at this point in time, and specifically wants her."

This suggested to the Doctor that he should stop running and let the monster take them to its leader — but, truth be told, he wasn't completely sure that would result in Seo's remaining alive.

Or his coming with her.

Best handle this with care.

"It wants me?" Seo sighed, irritated. Then, over her shoulder, shouted, "Everything in the universe wants me! Get in line!"

The monster lunged for her.

And the Doctor shoved her back behind him, whirling around to stand in place directly in front of the creature, and trying the sonic again. "Take me to your leader!" the Doctor demanded.

To his surprise, the monster reared back.

Howling in agony.

The Doctor looked between the monster and the sonic. Impressed. "Right setting must make all the difference," he decided. Blasted the beast again, and it reared up, clawing at the air as if it were possessed.

"Maybe it's deaf!" Seo proposed. "It never detected us based on sound, after all; it just kept sniffing! Perhaps the sonic vibrations rattled that sense of balance located in the inner ear?"

The Doctor beamed down at her. "Good thinking! Like it." He stepped forwards. "Let's make sure."

Seo gave an irritated huff at this.

The Doctor brushed it off.

"Now that I've got your attention," the Doctor said, stopping the sonic. He bounced on his toes, in front of the creature. "Let's start with the basics. I'm the Doctor!" He gestured his sonic at Seo. "She's Seo."

She gave another huff.

"But you already knew that," the Doctor said, turning back to the creature. "So. What are you doing, here, who are you working for, and…" He opened up his hands. "Take me to your leader!"

Buffy stuck the dagger between her teeth, climbing up the monster's back by clutching at different patches of fur. It reared back, claws scrabbling at the air, trying to shake Buffy off.

But she kept on climbing, towards the head.

She could hear Seo, in the background, explaining to the Doctor that she thought the monster was deaf. Buffy grinned.

Oh, go Seo!

Then came the Doctor, stepping forwards and introducing himself to the creature. Like he thought it could hear and understand him, and had the capability for intelligent thought.

No, Doctor!

Was this what he was like without a Buffy around to give him some common sense?!

Buffy grabbed hold of the fur more tightly, in her left hand, and plucked the dagger out of her mouth with her right. "Doctor, stop trying to talk to it!" she screamed. "It can't hear you! It's deaf!"

And, from what she'd seen in hell, just a guard-dog. Non-sentient.

But the Doctor didn't hear Buffy.

Just took a step back, as the monster howled, and muttered to Seo, "All right. Deaf. Point to you on this one."

"Do you ever listen to me?" Seo hissed.

"I listened fine!" The Doctor replied. "I just wasn't prepared to take your assertion at face value."

Seo glared at him.

And the monster lunged for the Doctor.

Buffy stabbed her knife in the monster's back, and it reared back, once more. Spun around, flinging Buffy away so that she slammed against the side-wall of the alleyway, hissing with the pain.

It sniffed for her.

But couldn't sense her.

It began to turn back towards Seo — but Buffy pulled herself to her feet. And launched herself into another flip.

This time, she landed right smack on the creature's head.

And thrust her dagger into the area behind the left ear.

The instant she did so… a shot rang out, behind her. The Yixolpot slumped, in place, whining as it died. And Jack Harkness, revolver in hand, stepped forwards.

Looking right through Buffy, as if she weren't there.

"You two okay?" Jack asked the Doctor and Seo.

Buffy yanked her knife out of the Yixolpot's head. "You fired a gun in front of the Doctor?" She shook her head. "You're so gonna get it now, Jack!"

Sure enough, the Doctor was already on at Jack about how he'd been trying to figure out what was really going on, here — and killing that creature wouldn't help him find out any faster, would it?!

Buffy grinned, despite herself.

Looking on at the Doctor, standing there, just in front of her — and yet he couldn't even see or hear her.

"I missed you, you know," Buffy told him. "You've got no idea how much…!"

She paused.

Her eyes lingering on his face. Watching the way he held Seo's hand — as if he couldn't bear to lose her.

"Thanks," Buffy whispered. "For looking after her."

"…and if I could think of another way, I would have used it," Jack insisted. He tucked the gun away, before the Doctor could snatch it from him and throw it into a volcano. "Hey, after it went through you, Doctor, it would have gone for Seo. And you told me to protect her."

The Doctor was loathe to concede the point.

But Jack had pretty much hemmed him in.

"Father's right, though," Seo said. "You shouldn't have killed it. You should have just wounded it, so we could figure out what was going on."

Jack slumped. "You too, huh?"

"Next time, we should put a… tracker on it!" Seo proposed. "See where it goes when it's injured and trying to get help. Maybe we'll see who's behind all these killings."

"At the very least, we should figure out if it the creature was an animal, or some robot sniffer dog," the Doctor proposed. He let go of Seo's hand, and raced forwards, sonic at the ready. "If we could just…!"

He paused.

Frowned.

The others turned, to face him. And then stared, past him.

"It's gone," said Jack.

The Doctor tapped his sonic against his lips. "A vanished body," he muttered. "A creature I've never seen before. Everything's gone wrong in the future, and it all stems from this point." He spun around. Pointing at Jack. "And then… there's you."

"Jack?" Seo looked in between the Doctor and Jack. Confused.

Jack looked confused, too, but was trying to hide it by being charming. "I'm in all the best stories," Jack said, with a wink.

The Doctor ignored him.

"I have these… theories," the Doctor continued. He gestured at his own head, with a flustered sort of shake of his hands. "Well, not theories, yet. More like… things. Things trying to be theories." He gave up the metaphor, frustrated. "How can a simple alien invasion on one planet destroy the whole future? What happens here that so fundamentally changes time? I have some ideas." He dropped the hand. "Problem is… Jack doesn't fit into any of them."

"Maybe the invasion leads to some scientist here developing a race of super-soldiers!" Seo tried. She pointed at Jack. "And they use something about him to make the soldiers immortal, and—!"

The Doctor saw the movement before Seo did, and grabbed her by the shirt-sleeve, yanking her out of the way. She only just barely missed being hit by the blast that intersected with the wall.

Jack spun around.

Seeing the figure darting away.

"I'm onto him!" Jack shouted, racing off into the distance.

"No, Jack, don't…!" the Doctor tried, but it was already too late. Jack was already gone. The Doctor stepped back, took Seo's hand in his. "Oh, Jack. It's pointless. There'll just be something else that shows up here, sooner or later."

Buffy was about to run after Jack, but stopped, when she heard the Doctor's words.

She spun back around.

"You've figured something out," Buffy realized. She charged back towards, him, analyzing his face. "Yeah — you've got this 'I'm-so-smart' look on, like you've just become Einstein or whatever."

"You've worked it out, too?" the Doctor prompted Seo.

Whatever the hell it was, Seo very clearly had.

Seo shifted, nervously. "Should we hide?"

"Hide?" the Doctor shook his head. "No. Hiding is for tortoises. Or snakes. Or… small furry creatures who burrow down into things." He grinned, flipping his sonic through the air and catching it. "Better idea! Let's hang around and see what happens next. Prove ourselves right or wrong."

Buffy didn't like that plan.

It put Seo in way too much danger!

But Seo — in typical Seo fashion — seemed to think it was brilliant.

"But are you sure they'll show up here?" Seo asked. "They didn't before you arrived. Jack and I went all over the place, and we never encountered any of these aliens!"

The Doctor's chirpy face fell.

"That's… a good point," he muttered. "And… very worrying."

They stopped talking, though, as a group of ghostly figures marched through the air just in front of them. Then, in a surge, faded into reality, as Cybermen.

"What?!" the Doctor cried.

Buffy was guessing that meant this proved his theory — whatever it was — wrong.

"You will be like us," the Cybermen declared. "You will be upgraded."

Other Cybermen marched into view, all pointing their guns straight at the Doctor and Seo.

"You will return the Cyberplanner," the Cybermen chanted, in unison.

The Doctor glanced about himself.

Then buzzed his sonic at the edge of the awning, stretched across the alleyway, above them.

The strings holding the canvas taught snapped, and the canvas flomped down on top of the Cybermen.

"Run!" the Doctor shouted, turning on his heels and racing off with Seo.

Buffy stayed behind, another minute longer. Okay, Cybermen. Cybermen. They were like… robots! Right? Buffy didn't know.

But she figured she had one shot at this.

She raced forwards, found the nearest fire hydrant.

And, moment the Cybermen came close enough, used her Slayer Strength to kick the top off.

Water shot through the air, splashing down on the Cybermen, making their circuits fizzle and pop.

"Upgrading," the Cybermen chanted, in unison.

And then they were off, again.

Still after the Doctor and Seo.

Buffy raced after them, trying to grab one back. It didn't see her, but used a metal arm to try to shove her aside — but she yanked at the arm, instead, bending down and using the momentum of the push as leverage to hoist him over her head and slam him against a wall.

The other Cybermen appeared not to have noticed.

Weird.

"Damn you, stupid robot things!" Buffy shouted, racing after them. "I may be a ghost, but I'm gonna haunt the hell out of you if you harm my daughter!"