Disclaimer: Sadly, I have no claim on Doctor Who and make no profit from it.

"Wha-? How did you…?"

"That's what the TARDIS is telling me. Unless she's fried a circuit in her old age." He punched a few more buttons and whacked something with a mallet. "Nope, she's still insisting. Says your energy signature is foreign to this dimension. But that's impossible!" He pointed an accusing finger. "You are impossible, Rose Tyler."

She laughed weakly. "Not impossible, just…highly improbable."

She bit back a yelp of surprise as he was suddenly inches away from her, running the sonic screwdriver across her face, his eyes lit up with the excitement of novelty and discovery. "You're scanning as human," he said after a moment, sounding vaguely disappointed.

"Yep, that's me, very much human, as a mate of mine used to like to point out all the time."

"But twenty-first century humans don't have dimension-hopping capabilities. So…future, then?"

"Nope. Twenty-first century born and bred. Well, not really, I mean, born and bred in the twentieth, actually, but I got to the twenty-first on the slow path."

He didn't appear to be listening to that bit of rambling, just smacked his forehead with his palm. "Wait, what am I saying? Future humans can't dimension-hop either. There is no species of any time that can travel between dimensions, not without tearing a hole in the universe."

"Time Lords can." She noted with satisfaction how he stilled, eyes widened, and took a step back when she named his race. It wasn't too often she could elicit that kind of surprise from the Doctor.

He studied her for a long moment, and then broke into another grin. "So I'm going to take a wild guess here and say that this isn't your first time in a TARDIS."

She grinned back. "Not my first TARDIS. Not my first Time Lord. Actually, not even my first Doctor."

She had managed to shock him again. Twice within ten seconds. Not bad for a human, Rose Tyler. "Wait, you know the me of another universe?"

"First time I met him, he saved me from getting me head chopped off by plastic dummies in Henrik's. And then I repaid the favor when we met the Nestene Consciousness. That's how I was pretty sure of where to find you, once I realized the same story was happening here."

"Well, that explains how you managed to think so quickly on your feet down there." He hooked a thumb vaguely in what she supposed was meant to be the direction of the now-defunct Consciousness.

"Oi! I thought quickly the first time around, too, thank you very much! Bloomin' great Time Lord brain, and neither of you can even see the gigantic transmitter right smack in front of you. At least he had the good grace to thank me for saving his sorry rear."

The Doctor managed a chagrined smile. "Quite right. Thank you, Rose Tyler. You were fantastic in there." He paused, then continued quietly, "So this other Doctor…did he just leave you here, then?"

She sighed. "That, mate, is a very long story. It would take a bit of time."

He settled back against the console and folded his arms. "I'm a Time Lord."

"Right." She sighed again, then hopped up into the jump seat. "Guess I might as well get comfortable…"

It was a long story, and it was painful to tell. The first accidental crash-landing, the one responsible for her contamination with Voidstuff; the Cybermen, whose existence was news to this Doctor ("You need to keep a closer eye on us, visit more often, mate; Earth needs you," she chided affectionately); Mickey's decision to stay and carry on the fight; the breaking through of the Cybermen and the Daleks to her world; the epic battle between them and the Doctor's desperate plan to halt it; her last-minute rescue from the suction of the Void by her parallel father. But she prided herself that she had managed to get through most of it without choking up. At least until the very end of the Battle of Canary Wharf. There was no way she could recount that without tears. She didn't even attempt to talk about Bad Wolf Bay.

The Doctor stared down at the fragile human, the silence broken only by her shuddering breaths as she tried to control the sobs that wanted to break forth. Was she always weepy like this? Her story made clear how she had gotten here, but not why she was still here. Although she hadn't said it in so many words, her feelings for her Doctor were obvious, even to him to whom human reactions were so often a fascinating mystery. Maybe she had gotten too clingy and he had seen the chance to take back his freedom, free from guilt, leaving her safely in the arms of her family. She wasn't clingy back there when you were dealing with the Consciousness, part of him reprimanded. She didn't play the damsel in distress. She was collected and competent and she got the job done without fuss. But the fact remained, however accidental or even tragic the circumstances of her landing in this universe were, this other Doctor had not come for her, had not tried to bring her back.

She looked up at that moment, swiping with embarrassment at her tears, and managed in something akin to her normal voice, "But now that I've found you, you and the other Time Lords – you can get me back where I belong, can't you?"

His stomach knotted at the hope glistening in her eyes. Sure he could, but would the other him thank him for it? He himself had had many companions over the course of his travels. He had felt affection for them all, and some he missed more than others, but there was none from whom he would have welcomed the desperate yearning that Rose so clearly felt, nor for whom he would have returned the feeling. Wasn't she better off here, with a mother and a surrogate father and a best friend, than traipsing off to another universe in search of someone who clearly couldn't be bothered searching for her? Even if she didn't have a propensity for clingy domesticity, the other Doctor must have good reasons for not wanting her back. He cleared his throat. "Rose, this is going to come out sounding much harsher than I mean it to, but…if you belong with him, why doesn't he come get you himself?"

She stared down at her hands for a moment, and he wondered if the truth of rejection had finally hit her. But when she looked up again, there was a fire in her eyes, a blazing pain, and the Doctor instinctively knew that it was not sorrow for herself but for another, for one she loved so deeply that his pain was hers. "He can't. He would if he could, but he can't. He said that it needed Time Lords to travel between universes."

"Yes." But her Doctor was a Time Lord, wasn't he? He was confused.

"Time Lords, plural."

"Yes." He wasn't quite sure where this was going.

"In our universe, there are no more Time Lords. He is the last one. He is all alone."

He had to grip the console to keep from staggering. "How…how is that possible?" His brain, his gigantic, brilliant brain that could perceive the whole fabric of space and time, was having trouble wrapping itself around this concept of aloneness, of singularity.

"There was a war. A Time War. Between the Time Lords and the Daleks." His breath hissed out at that name. He had had his own bad experiences with Daleks. But, he suddenly suspected, nothing like his counterpart had had. "They were all destroyed. Everyone. All the Daleks – well, nearly all. All the Time Lords. Gallifrey. All gone. The Doctor was the only survivor."

"Gallifrey…?" he whispered.

"Burned, he said. Time Lords – extinct." Gone was the fragile, weeping woman. Her voice was harsh, merciless. She was trying to make him feel what the other felt. "No stopping off for a visit home, no popping in to see mum and dad. And no one to help him travel to this universe to retrieve the one person left who truly knows him, who makes him feel like he belongs somewhere, belongs to someone, is connected to the world. Try to imagine, just try to feel what that feels like to him, what it is like to be completely alone in the universe, alone in your own head." She was out of her seat now, standing in front of him, and she laid her palms against his hearts, and he could feel it, feel the isolation and the horror and the despair choking him as if they were his own. "I am pleading with you, take me back there, for my sake, yes, but for his too, because he could be you. Because he is you."

He stared, mesmerized, for a moment, and then gently caught her hands in his. "It's not easy. I don't know what he told you, how he made it sound, but it's a complicated, tricky process."

"But it's possible?"

He hesitated another moment, but he couldn't hold out against the fierce determination in her unwavering gaze. He suddenly broke out into the huge grin, the one she remembered so well, the one that said, 'This will be hard, and this will be dangerous, and won't that be fantastic fun?'