The Doctor watched the other TARDIS take flight, having promised his older self that he would meet him at precisely 14:30 at the Gallery. They could all do with a cup of tea after the day they had. But he was unprepared to leave just at that moment; there was something more he had to do.

The ship disappeared into the vortex, leaving the hut looking so much larger than it had before. It smelled of dust, the air was thick with it. Each step he took rustled against the straw strewn floor.

He felt very alone.

"Rose?" He whispered, and all at once cursed himself for his stupidity. He must have looked pathetic. Calling for the long lost girl somewhere she couldn't possibly be. Hoping.

"He…I…I said Bad Wolf. You must have been here…somehow. I know it."

"My clever boy." The blood rushed away from his face as he turned. There she was. Leaning against the TARDIS, her smile infectious and her eyes glowing. His mouth opened and closed wordlessly, his breath catching in his throat.

"Rose…" He wanted to move but he couldn't. His body wouldn't listen. She laughed, passing a hand through her hair.

"What…How?" He found his strength and moved towards her, arms automatically outstretching to encompass her body against his. But his palms only connected with the wood of the TARDIS doors.

"I'm still just an image. No touch." She teased, somewhat ruthlessly. He turned again to find her behind him.

"I don't understand…Rose-"

"Not quite, clever boy." She smiled. Her eyes widened, mouth open, waiting for him to realise.

Oh…this wasn't fair.

"You're the interface." He whispered, his hearts dropping with the weight of its cruelty.

"Bingo." She whispered the word, drawing it out and tasting it on her tongue. His clouded mind found the emotion he was searching for. Rage.

"Why are you still here? Eh? Why are you here, to torment me?" The Interface frowned at him.

"I'm here for you."

"Then why did you choose her? Why her?" His voice was strained now, echoing around the empty room. The interface looked to the ceiling, frowning in concentration, obviously searching her data banks for the right answer. If he looked closely he swore he could almost see the numbers speeding through her soft brown irises. Finally she smiled.

"She's the most important." He scoffed.

"What does that mean, the most important? Plenty of people were important to me. Plenty! Romana…Susan…Donna…Why her?" Even he knew the blasé tone sounded disbelieving. She knew it too. Clever girl.

"She's the most important." She simply said again. The Doctor swallowed hard, grasping in his pockets for his glasses. He whipped them on and stepped forwards; so close they were nose to nose. His eyes scanned her form.

She was the same but different. A little too perfect. Her eyebrows too perfectly shaped, face too symmetrical…but those eyes. Those eyes were the same. How could a machine capture the raw power of Rose Tyler in just those eyes?

"You're going to die. Soon." He broke his gaze, looking at the dusty floor.

"I know." He whispered. He jumped as he felt her soft palm grasp his own.

"Don't deny yourself this…It will be your last chance." He couldn't tear his gaze away from her fingers entwined with his.

"I thought you couldn't touch." He whispered, his voice hoarse. She shrugged.

"I changed my mind." He allowed his fingers to grasp hers a little more firmly, and in doing so felt something hard and cold wrapped around her finger. He brought it to his face and words failed him as he saw, what was undeniably, a wedding ring. Dropping her hand he growled.

"What a delightful little detail you added." The Interface looked confused as she gazed down at her hand.

"I'm wearing a wedding ring? Huh…My, my she has been a busy girl-"

"Shut up." The Interface gasped in mock horror as she circled him.

"Is that any way to talk to your wife, Doctor?" She stood on her toes to whisper in his ear.

"She was never my wife, she was never…" With a sigh the Interface moved away to sit on forgotten wooden crate. It groaned under the weight of her. The Doctor frowned…it shouldn't groan…she should be weightless, in theory. She wasn't real.

"For a clever boy you can be a little slow. Have you not ever wondered just how much of her was left in the TARDIS after she became the Bad Wolf? Just maybe I'm using that connection to connect to her? Or maybe I am her? Or maybe…this is all in your head…" She whispered at the end, wide eyed and almost genuinely confused.

"That's impossible. She's worlds away, literally, in another universe. Impossible."

"And bringing three Doctors together should have been impossible…But I promise you, Doctor, you've never met a girl like me." He gave up, throwing a hand in the air.

"I don't like riddles."

"No…But you like her. You like the way she looks at you in the morning, all bleary eyed and adorable…You like the way she brings you tea in the morning, made perfectly each time. You like the way her lips feel against yours-"

"And that's where you're wrong!" He pointed a finger at her, accusing and vengeful. How dare she.

"I never knew those things. Never. You're not her, you're nothing but a cheap imitation of what Rose Tyler was. Is." His voice shook at the unfairness of it all. Like she was being dangled on a thread in front of him only to find the thread was really a noose. Waiting.

The Interface paused.

"You're right…you didn't know those things…But she does. Wherever she is, she knows those things. I can see into her head."

"No."

"Yes." She hissed at him, but not unkindly…almost insistently. Hopping from the crate she stood before him once more.

"I'm trying to be kind. This is your reward."

"My reward for what?" He spat, praying for her to stop talking, to stop haunting him. But the pain was sweet somehow. A part of him didn't want her to stop. It felt so good just to hear her voice again…

"For those 2 billion children, Doctor. You chose to save them. This is your reward." He shook his head and laughed mirthlessly.

"This is no reward. This is cruel." The Interface stood directly before him, and for a mechanical consciousness did a great impression at looking hurt.

"Don't you see? You need this. So many things unsaid, so many things never spoken of…You need this. Talk to her. Tell her. Who knows, maybe she'll hear it, like a whisper in her dreams."

"You're not her though. It wouldn't be right." She looked at the ground and pursed her lips before smiling that Rose Tyler smile.

"Maybe I am her….But you could pretend. I won't tell." The Doctor gazed at her; underneath the wild hair and smoky eyes it was still her face. He remembered gazing at that face everyday; he had memorized it so many times that it was almost more familiar than his own.

"What do I say?" The Interface looked at him sadly.

"Whatever needs to be said." The room was silent for a long time as she stood, waiting. How could he even begin…He had no idea.

"I can't." He finally said, almost ashamed of himself for being struck dumb. Her eyes searched his for a moment, before glowing a brilliant gold. It was dazzling really.

Then he heard it. The soft Jazz of the Moonlight Serenade…seemingly coming from the very walls surrounding them. She grasped his hands, placing their bodies into the familiar position they had donned all those years ago.

"Show me your moves." She whispered into his ear. They swayed slowly in the room together, the memories of the War and the struggle melting away until it was just them. Rassilon, she even smelt the same.

"I miss you." The Interface whispered. The Doctor tried hard to keep his composure, not daring to hope that she would hear. Maybe it was a lie. Maybe it was a trick. But somehow he was struggling to care anymore.

"I miss you too. I…" He stopped, unwilling to divulge more. The Interface grasped him tighter, still swaying to their song.

"Tell me."

"I find myself talking sometimes. To you…And then I look up and you're not there and it hits me like a supernova. That you're gone. The worst part is not that you're gone…it's the forgetting that you're gone that hurts most." She laughed a little.

"How do you think it feels for me, waking up to your face everyday? I forget that you're gone because you're always with me, still. And it hurts sometimes…I feel guilty." The Doctor frowned into her hair.

"But you're happy? Aren't you, you're happy?"

"The happiest. I have you, and that's all I ever wanted. It just hurts that you…this you…you're alone." The Doctor sighed.

"Last of the Time Lords. Same old story for the rest of time." He could feel her melt into him just a bit more, craving to surround herself with him.

"But I was going to stay with you…Forever." Oh, that promise. The one promise she had broken. The one promise that would haunt him for the rest of his life.

"I know. I wanted you to…But do you understand, why I left you? Why I had to?" He was desperate now.

"Yes…Doesn't make it hurt less, but yes."

"And you know why I can't say it." He pushed her, and there was nothing but the dulcet tones of the Serenade for a few moments.

"Yeah." Her voice was so small he almost missed it.

"I still need you, Rose. I'm scared. I can feel my mind slipping, somewhere dark and…I did something terrible. A woman died and it was because of me. She would rather have killed herself than let me become a monster." She hushed him.

"You're not a monster. You're lonely. And you've suffered, more than anyone I've ever known. You need someone." He shook his head, unwilling to accept what deep down he knew was the truth.

"I don't think I can do that again. Have someone travel with me…live with me…not full time anyway."

"This is why I worry about you, Doctor. You need that."

"But I can't take the goodbye. Not again." She had no answer to that.

"How was the wedding?" He almost didn't want to ask, the thought of the could be and never to be cut him almost like a dagger.

"Wonderful…though you wouldn't change out of those Converse, not even for the ceremony, and mum nearly threw a fit." For the first time in a while he laughed.

"Ha, would love to have seen that."

"Mmm…You proposed to me in Barcelona, you know. The place, not the planet."

"Sounds like I did well."

"You did." The music was trailing away now, but he didn't want to stop…Not yet.

"Do you ever wonder what it would have been like if I'd stayed?" Of course he had. In the darkest nights he thought of all the places he should have taken her, cursing himself for all the wasted time.

"Every day. It would have been…"

"Fantastic?"

"Yeah."

"I'll always love you, Doctor. He's you…and you're him, and I'll love you both until I die." The Doctor squeezed her a little tighter.

"Don't say that…Rose Tyler, you're invincible. You'll never die."

"Of course, how could I be so stupid." It was a lie. Of course they both knew that. But a lie was better than the truth.

"The longer I stay here the harder it is to leave." He whispered, knowing their time was almost up.

"I know."

"Just remember, Rose….That you saved me…You took me and made me better, you showed me what it was to be human. And that's what I needed, my entire life. I acted like I was above it all, but chips in a café…Your mum's cooking…Christmas…Those were the best days of my life. And I'll never forget that. The Interface is right, you are the most important." He thought he heard a small sob into his lapel.

"Will you ever forget me?"

"No. I've seen my future, I've seen him. And I know he acts like he's forgotten everything, all the pain, all the people who were important. I know he'll never mention Donna, or Martha…Jack..Mickey…You. He'll never speak of them out loud again. He'll pretend he doesn't remember. But the Doctor lies. He remembers. He'll always remember. It just hurts too much."

He lifted his head from the soft bed of her hair and looked into his eyes. And there she was. It was her. Staring back with wide tear filled eyes. It had to be her. No machine could ever be this good an imitation.

"I don't know if you're the Interface…I don't know if you have Rose's memories or if you are her. But I hope you hear me when I say this…I will never forget."

"I hear you. I promise." A tear fell from her eye and a crease appeared in her brow. And he believed her. He stepped back, untangling himself from her soft form.

"I need to go. I've still got a little life left in this body." He feigned nonchalance and Rose laughed.

"Go on. Go be the Doctor. Save a few worlds while you're at it." He gave her a tight smile and stepped towards his ship.

His hand hesitated on the door. The sight of her standing, alone, in the small hut made her look vulnerable….It felt sorely like he was having to leave her all over again….She gave him a sad smile.

"Your song is ending, Doctor. Promise we one thing?" He felt a burgeoning tear in his eye that he blinked away quickly.

"Anything." She smiled that Rose Tyler smile one last time and all at once his hearts lifted.

"Make it beautiful. One last soaring song." Lips pursed hard he nodded.

"For you, Rose. I promise." He tore his eyes away from her and slammed the TARDIS doors shut. As the grinding and whirring of flight filled the room, Rose Tyler gave her old home one last tearful smile.

"Time to go home now, Rose." The Interface whispered, a flash of light filled the room and then she was gone.