As the regeneration energy started to pulse in a golden light out of his hands, the Doctor eyes teared up, and an anguished expression filled his face.

"I don't want to go," he cried.

He didn't want to go, because then he knows he will never see Rose again. And that's exactly why he had to die – he'd sent her off to someone else, his lucky doppelganger, and now his own chances of ever being happy with her are gone – there's nothing left for this regeneration to live for. Even when she was gone, before she'd come back, he'd had hope. He didn't try to get back to her – he didn't dare try, he knew it was supposed to be impossible. Nonetheless, he'd waited for her. He waited to see if, as always, something wonderful and impossible would just happen. He should have known that she would not be so passive. She'd once torn open the TARDIS with a tow truck to get back to him… why should a parallel universe stop her? But now, it really was impossible, not because the parallel was closed off, but because he'd chosen not to say those three words, had let the doppelganger take his place, because he knew it was better for her. And now he could never go back, because it would just confuse her and ruin his gift to her – a happy life. And that is why he had to die… he had no hope left. Even this chance to see her one last time, to see her beautiful smile, was both a wonderful gift and a horrible curse – because no matter how warmly she greeted him, almost like an old friend, she still didn't know him, he still couldn't open his arms and wait for her to fall into them like she had so many times before, and that, that, really killed him.

…..

Rose and the Human Doctor were happily working in the Torchwood sub-basement, tinkering with the console that was rebuilding the TARDIS. Already, in the middle of the circular space in the middle, a square frame, with the beginning of some blue planks of wood, was starting to sprout up from the floor. The Doctor said that it pretty much grew on it's own, but nonetheless they liked to come down here to check on its progress, to press buttons and pull on levers to feel like they were helping it along. That, and they liked this space more than their gorgeous, windowed, professional office space. This was more… them—not to mention more private (the work tables were often used for more than just "work"). Just the fact that there was a TARDIS growing in this space, that the room was filled with Time Lord tech, made it feel more like they were at home in the TARDIS itself, like the good old days.

They were standing around the console, chatting and laughing and smiling at each other in their lovesick way, when suddenly the Doctor groaned and bent over in pain. Rose reached out to support him.

"Doctor! Doctor, are you okay?"

He just groaned, trying to sputter out some words, but could barely get them out through the stabbing pain in his gut.

"I… don't… I can't…"

"Ssshhh, sshh, it's okay, we just have to get you up to the sick bay, that's all…"

The Doctor groaned in disagreement. He wasn't sure what they could do for him, and anyway, he didn't think he could even make it to the elevator. He gestured to the nearest work table and started to hobble over to it, with Rose's help. She helped him lay down on it, as he continued to clutch his stomach in pain.

"Doctor, please, tell me what's going on."

"Rose, Rose, I… I love you…"

"No, shut up, you're not dying, don't say that… just tell me what's happening to you."

"He's… he's regenerating…"

Rose just stared at him in shock. Her first thought was for the original Doctor, the idea that he would never again be in the same form that she had been so in love with. But she quickly dismissed that thought, to think of the man in front of her, the one she loved now. What did this mean for him?

"What… what will happen to you?" she said, as she began to cry.

"I don't know…" He reached up his hand to rest on her cheek, and look up at her face with tears in his eyes, drinking it in, in case it was his last look.

Suddenly, they saw the regeneration light that they were so familiar with.

"No!" Rose cried, "no! You can't!"

But the light was different. Instead of emanating outward from the Doctor, it seemed like it was appearing out of thin air, and being sucked into his skin. But just like a typical regeneration, it started with a light, eerie glow around his hands, and then his face. "Rose, stand back!" She backed up just in time, as the light exploded in a blinding burst. But, once again, the light was sucked inward, rather than exploding outward. Rose looked on in horror, terrified that it would kill him.

It was over as quickly as it began, and the Doctor lay on the table, still, with his eyes closed. Rose sobbed, and approached, running her hands all over his face and body, crying. "No, no, it can't be, oh god you can't leave me!" Suddenly, the Doctor gasped and sat bolt upright. Rose jumped back in shock, and then came forward and clasped her hand to his chest. His heart was beating like mad, but there was still just one.

The Doctor looked at her in confusion for a second and then back down, breathing rapidly. Suddenly his eyes shut as a flood of memories flashed through him. A desert planet and an abandoned bus. A Martian space station. Wilfred, and the Master. It was over in a second, and he opened his eyes.

"Oh!" he exclaimed, clutching his head.

"Doctor! Doctor, are you ok?"

"Oh yes," he smiled up at her.

"Doctor, what was that?"

"He regenerated, Rose. And the last thing he thought about, the last person he saw, was you…"

She froze.

"Do you remember? New Year's Eve, 2005?"

She froze, her heart beating rapidly. She remembered.

"He just wanted to see you one last time before he…"

"How do you know this?" Rose snapped, on edge. She didn't like to think about the original Doctor, because she worried thinking about him would make her own human Doctor, and her love for him, somehow less than… but now that that version of the Doctor is gone… he's gone!

"His memories since we split… they sort of came to me. That and…" he hesitated.

"And what?"

"And a bit of his soul. The bit of his soul… that loved you."

Rose stared, confused and anxious and emotional. The Doctor responded by reaching out to her, clutching at her face and pulled it close to his, looking directly into her eyes. Rose saw it, in his eyes, that bit of sadness that her Human Doctor always lacked. She gasped a little.

"There's an old Gallifreyan myth… I always dismissed it as an old wife's tale, a bit of superstition. Just like humans, each regeneration has its own unique soul… when that regeneration dies, the soul leaves the body and goes elsewhere, also like humans. The myth is that the soul travels to where it most desires to go. Normally the Time Lord soul just floats around in the ether, but this soul had a handy bio-matching receptacle to make it's home… a receptacle that happened to be right where it wanted to be… Rose…" he reached out and took her hand, and held it up to his lips and kissed it fervently. He looked at her with love in his eyes.

"What… what does this mean… for him?"

"It means he can move on… Rose, he was so haunted by having to leave you, and Donna… he was falling apart. He couldn't go on living like that, with the guilt, and the heartbreak, and the loneliness. Now he can start over… just like us."

He smiled, and she half smiled back, shaken by this emotional information. But she thought about how lucky she was, the incredible gift the Doctor had given her, this life she had now. She couldn't bear to think of the Doctor unhappy, and if he had to regenerate to find peace, and happiness, how could she begrudge him exactly what he had given her? She brightened up, vowing to come to terms with the idea that her old Doctor was gone. But she was lucky enough to him right here with her anyway.

"Come on, you," and she helped him off the table, as he was still a little weak and shaken. "Let's get you a cup of tea."