As the TARDIS faded into nothingness, the Doctor took hold of Rose's hand and turned to her. His face was closed and inscrutable. She couldn't tell what he was thinking. As she looked up at him, the tears brimming in her eyes welled up and spilled down her cheeks. He lifted his free hand and brushed them away.

Her eyes searched his face, drinking him in. She felt so torn and confused; he could see it in her eyes. She was clearly sad, happy and baffled, all at the same time. It was no different to how he felt, but seeing the confusion and hurt on her face made his hearts twist in his chest.

No, not hearts. He had to keep reminding himself he just had one heart now. He should have had at least a couple of regenerations left, a good two or three hundred years give or take a decade or so. But now he had what, about sixty years left, if that? It was a strange thought, but not something that bothered him too much. Not that long ago he'd have gladly traded everything he had for just one more day with Rose. He'd missed her so much that the pain had settled itself into him, becoming part of him in a deep, elemental way. They'd not had much time together; there was so much more he'd wanted to do with her, so many more places he could have taken her.

Now his alternate self had made off with the TARDIS, he wouldn't ever be able to take her to new places again. He'd really miss the way that her eyes blazed with excitement when she stepped onto a new planet; the way her face lit up, ready for an adventure.

Rose looked at the Doctor: the "new" Doctor, but he wasn't new, not really. Every line, every mark on his face, the way his eyes crinkled at the edges, the way his soft brown hair ruffled in the breeze; he was the same. Her heart flooded with happiness, but then she felt it drain away abruptly. He was staring at the spot where the TARDIS had been with a look of loss and pain on his face.

She let go of his hand.

"He doesn't want to be here with me," she thought. "He wishes he was back on the TARDIS. After all, he didn't really get a choice; he got left here, just like I did."

The Doctor looked down at her in surprise.

"Rose?" he said, softly. "What's the matter?"

She just shook her head, beginning to cry again. He put his arms around her, but she didn't do the same to him, though she did press her face against his shoulder. He reached up to stroke her back. She was so tense.

"She doesn't want me," he thought. "Even though I'm me, the same me, she wants the other version. How can I convince her that I'm no different? My other self said I was dangerous, a throwback to how I was at the end of the Time War, but how can that be true? I still have my memories. I was there on the street, running toward Rose, I remember the Dalek shooting me: the pain, lying on the ground, being taken into the TARDIS. Next thing I know, I'm sitting on the floor, naked, with Donna staring at me. I admit I felt a bit odd, a bit, well, human I suppose. But I'm still me. On the Crucible, Donna said I should wait for the Doctor before deciding to destroy the Dalek fleet. But I am the Doctor! And anyway, there was no choice to be made. That Dalek fleet would have invaded and destroyed every inhabited planet in the Universe. I couldn't have let that happen."

He was frowning, lost in his thoughts, looking out to sea, then realised that Rose was still crying and that he needed to at least try and lighten the mood. He gave her a squeeze, and tried to inject a jovial note into his voice.

"Well then, here we are: Dålig Ulv Stranden. I know it's poetic and everything: I get that. But I wish I'd not decided to leave us here; it's miles away from anywhere. Sometimes, I just don't get me. I mean, why didn't I just drop us round the corner from your place?"

He pulled away, leant back, looked at her and grinned: a cheeky, disarming grin that almost knocked Rose off her feet. It really was him, her Doctor. She reached out to him and he took her hands in his, still smiling. Then his smile faded, and he looked serious again.

"Rose I, I don't know what I'll do now, but if you'll have me, then..."

She didn't let him finish.

"Of course I'll have you!" she said through her tears. "I mean, remember Krop Tor? We thought we'd lost the TARDIS then too, but it was ok."

"Yeah," he said, smiling. "You said that you didn't mind, that being stuck with me wasn't so bad. Made me feel pretty good, when you said that. I mean, as good as anyone can feel when they're stuck on an impossible planet held in a geostationary orbit around a black hole!"

"Yeah, but it was exciting though, wasn't it?" she said, and immediately wished she hadn't.

The Doctor looked grave, and let go of her hands. He looked down, sighed and kicked at the sand with one battered trainer.

"I can't take you anywhere, Rose. That's the only thing that bothers me. There's so much more I would have liked to show you, but I can't...not anymore."

Rose looked at him, exasperated.

"Doctor, do you think that the only reason I fell in love with you was because you could take me to other times and planets? I've already seen so much with you, I mean, werewolves, ghosts, Cybermen, Daleks. Not to mention all the other things we've done!" she said, laughing. "Do you remember that planet we went to? The one with twenty moons, and each one was a different colour. The grass was blue, and the sea was that lovely shade of purple. Oh, and those silver mountains. Almost forgot about them! They were gorgeous."

"Myriad 5," he said with a grin. "Yeah, that was good."

"So you see, I've been places with you that I'd never have got to see otherwise, and I loved travelling with you, I really did. But, at the end of the day, it's not planets or aliens or adventures that made me love you. It's you, everything about you."

She looked up at him and smiled, and he read the truth of what she'd said in her eyes.

Hearing her say that she loved him made all his doubts and confusion float away. He leant in and kissed her, more deeply this time. The kiss was gentle and intense in equal measure, and Rose felt her heart leap in her chest. Eventually she pulled back and looked up at him. He smiled and his eyes creased at the edges, full of humour, wisdom and depth. She could really get lost in those eyes. She suddenly realised the truth of that clichéd old saying about how a person's eyes are the windows to their soul.

"You're you, aren't you?" she whispered. "I mean, really you."

"Correct-a-mundo!" he said, then groaned. "I made a promise to myself I'd never use that word again. I just can't pull it off."

"No, you really can't!" she said, laughing, and kissed him again before he had a chance to reply. Then from behind them came a familiar voice, which had the same passion-killing effect as a bucket of cold water.

"Knock it off, you two!" said Jackie.

They leapt back from each other, startled. Rose looked over the Doctor's shoulder and blushed.

"Mum!" she said, embarrassed. The Doctor span round.

"Jackie!" he yelled, grinning. He grabbed her hands and whirled her around, before giving her a peck on the cheek. She laughed in spite of herself.

"Oi! Cut it out! I've spent the last quarter of an hour wandering around climbing on rocks, trying to get my phone to work."

"Did you get hold of Dad?" asked Rose.

"No, you're kidding aren't you? There's no signal, we're in the middle of nowhere. We'll have to walk to the nearest town. Are you two lovebirds ready to set off now or what? The tide's coming in."

The Doctor laughed, and grabbed Rose's hand. They followed Jackie and started to walk along the beach, back towards civilization. Every so often he'd look at Rose and smile with a happy, amazed look on his face. His giddiness was infectious and Rose couldn't help but laugh. He was just like he'd been before she'd been parted from him, on that awful day in Torchwood Tower.

She'd not felt the same lightness in the other version of him, the brown suited, grim-faced Doctor. He was still her Doctor, she knew that. But he had seemed different, older somehow, more serious.

The Doctor who was with her now was more like the person she remembered, the person she'd carried with her in her heart during the two long years they'd spent apart. Thinking about the other version, she now realised how deeply losing her must have hurt him. It had taken away some of his spark: the cheeky, joyful excitement that she loved about him, and which now seemed to be back with a vengeance judging by the way he kept stopping every few seconds to spin her round, hug her, kiss her or occasionally a combination of all three. Jackie was showing her tactful side for once and was walking far ahead of them, clearly trying to give them a bit of privacy.

Rose daydreamed and made plans as they walked. They'd need to hire a car and head to Bergen to catch a Zeppelin home. A plane would be faster, but she liked the airships; they were a great way to travel, quiet and environmentally friendly. They flew much lower than a plane so you could see everything as you passed over it: famous landmarks, towns and rivers, you name it. It was great, gorgeous. She often wondered why they weren't used in her world, her original world that is. This world was so familiar now that she'd started to take its oddities for granted.

Just like she accepted the Doctor's quirks. "Guess people just get used to stuff," she thought, and smiled.

The Doctor returned her smile and grinned again, then squeezed her hand.

"Penny for 'em?" he asked.

"I was just thinking how people can get used to pretty much anything."

"Yeah, you humans are an adaptable lot. Well, I say 'you humans' but I guess I should start saying 'us humans' now, shouldn't I? I'm part human now after all. Dunno which part exactly."

He grinned, but underneath he seemed a bit troubled.

Rose looked worried.

"Are you ok about it? I mean, you regenerate, and suddenly you're a different species, well, partly. Must have been a bit of a shock."

He looked at her, wondering what she must be thinking.

"I'm still the same, Rose," he said gently. "It's just, without my other heart I'm not going to regenerate again, ever, and that's a bit strange for me. Regeneration is…was…part of who I am. It'll take some getting used to. I'll have to be a bit more careful, for starters. Look after myself a bit better. No more chips!" he said, then grinned. "Nah, only kidding. Gotta have chips!"

Rose frowned.

"Do you wish it hadn't happened? You know, becoming part human?"

She bit her lip and looked away from him, not meeting his gaze. He reached down and took hold of her chin gently, tilting her head up, forcing her to look at him. He brushed her lips lightly with his own, then pulled back and gazed deeply into her eyes.

"Rose Tyler, I've been around for over nine hundred years and I can honestly say I've never been happier than I am right now, standing here with you. This is a gift, an amazing gift. I get to be with you, grow old with you, something I never thought would be possible. It's the ultimate adventure: one that I never thought I'd be able to have. Don't ever think that this isn't what I want, you're...you're..."

"Brilliant?" said Rose with a cheeky smile. He laughed, and kissed her again. His arms came up and wrapped around her, pulling her against him. She revelled in the feel of him, the taste of him. He was hers, finally. He even smelt the same, a soft, delicate, slightly musky scent that made her think of freshly mown grass.

It was intoxicating; she'd missed him so much. As their kiss began to heat up, she pressed her body against his. He made a low, involuntary growl of pleasure and reached down to run his hands over her hips. She felt the sound as well as hearing it; it vibrated against her lips and sent a hot, electric buzz running down her spine, making her tremble and push herself even closer to him. He deepened the kiss and she felt his tongue tentatively touch hers. She moaned softly and reached up to tangle her hands in his hair, tugging on it, pulling his head closer...

Then suddenly she was all too aware of where this was going and the fact her mum was just up ahead, and she very reluctantly pulled away.

"Plenty of time for that later," she said with a foxy, cheeky smile. He laughed and let her go.

"Is that a promise?" he replied, then immediately frowned and looked awkward, as if he'd just crossed an invisible line. She saw his discomfort and couldn't help chuckling.

"Hey, come on; don't go all shy on me now. It's taken me all that time just to get a snog, don't start playing hard to get again!" she said, laughing.

But he seemed determined to keep things serious. They carried on walking. He was looking straight ahead as he spoke.

"Rose, the reason I never, well…you know…was because I just didn't think it would be fair. I can't tell you how many times I've wanted to throw caution to the wind and just take you in my arms and kiss you, but I couldn't. What could I have offered you? Roaming the universe, getting us into trouble, never settling down. Not to mention the age difference: 903 and 20? Half the time I felt like a dirty old man for even thinking of you like that. So I fought it. Every day was a battle against my feelings, I hid them, tried to pretend that I didn't love you, that we were just mates. And it was hurting you, I could tell."

He looked at her then, and saw tears in her eyes.

"Yeah," she said, after a few seconds. "It did hurt a bit. But I was with you, so it was ok. I got to see you every day, live my life with you. Last time we were here, when you faded away and disappeared, I felt how apart we were: me trapped here in this other universe, I thought I'd die, I really did. God knows what I would have done without Mum and Dad, and Mickey too. They watched me round the clock, kept me safe. They helped me survive. But there was also this little, tiny bit of hope, the hope that maybe, somehow, I'd see you again one day. And that's what kept me going more than anything."

"Rose," he whispered, and stroked her face. "I love you."

"I love you too," she said. And they kissed yet again; for so long that Jackie was just a dot in the distance by the time they broke apart. Laughing, they ran after her hand in hand.

Just before they reached Jackie, he turned to Rose.

"You're holding my special hand, by the way. I love this hand!" he chuckled, but Rose looked a bit alarmed for a second and let go.

"What do you mean?" she said, although she wasn't sure she really wanted to know.

He held it up and wriggled his fingers playfully.

"It's the one the Sycorax cut off. Donna touched it just as the TARDIS was about to be destroyed. That's what triggered my second regeneration. It didn't half freak her out. She said I was bonkers!"

He laughed, remembering how surprised she'd been.

"I'll bet! Doctor Donna. She was amazing." Rose laughed too, and then frowned. "Is she going to be ok?"

The Doctor suddenly looked very serious indeed, becoming more like the other version of himself for a second.

"I wish I'd had the chance to say goodbye. Donna was great. Really great."

"She was. I'm glad she's with the other you. I don't like to think of you...him...being on your own out there."

The Doctor said nothing. He didn't want Rose to know that there was a chance that the alternate version of him could end up alone, it would upset her too much. He knew that Donna couldn't absorb that regeneration energy; humans just weren't built for it. He hoped his other self could find a way to save her that didn't involve wiping her mind, but it was the only thing he could think of that would have a chance of working. In fact, part of him could still faintly sense what his other self was thinking, just barely. Once the tear between the worlds healed, he knew that connection would fade.

But for now, he could still feel the other him, and he was hurting deeply. He didn't doubt that it was because of Rose, but he also got the sense that he'd lost Donna too, although whether she'd died or had simply been made to forget her adventures with him, he didn't know.

Then, it suddenly occurred to him that if he could still feel the other Doctor, that meant his other self could sense what was happening here too. He took Rose's hand and placed it on his chest, holding it in position.

"What...what are you doing?" she asked, looking confused.

He looked deep into Rose's eyes and focussed his mind on the other version of himself, allowing the other Doctor's pain to well up until it felt like the two halves of him were together again. He waited until he was sure the connection was at its peak, until he could almost make out the shadowy outline of the TARDIS around him, like a ghost. The beach was still visible, but it had faded slightly.

Looking down, he saw that a faint hint of brown was visible in his suit. As the connection peaked and he felt himself merge completely with his other self, he leant in and kissed Rose more deeply than ever before, drawing her against him so tightly that for a second she seemed to merge into him as well.

In the TARDIS, the other Doctor froze in shock, unable to believe what was happening. He closed his eyes to boost the faint, ghostly sensation of Rose's lips on his. Without even thinking, he kissed her back. At the same moment, the connection between him and his other self seemed to surge and suddenly he could see her too. He was on the beach with her, just for a second, and time seemed to stop as his mouth found hers again and they shared an awestruck, searching, passionate kiss. The two Doctors became one, just for a moment, but it was long enough.

"I love you," he said. "I always will." She leant back and looked into his eyes, amazed and happy. Then, the gap between the worlds began to close and the shadowy shape of the TARDIS around her began to fade. But just before it closed completely, she saw some of the pain in his face lessen. Some of the seriousness in his eyes drained away and he smiled. Then the last of the brown faded from the blue suit and the Doctor was divided again. But she finally knew for sure that he was still the same.

Some of the "new" Doctor's happiness had passed into the other Doctor, and she could see that the new Doctor had taken on some of his counterpart's pain in return. The Doctor looked sad for a second, but it didn't last long, not with Rose standing in front of him, looking so alive and beautiful and brilliant.

He laughed, picked her up, kissed her and spun her around until she was giddy and laughing and crying all at the same time. When he finally put her down, she took his arm and leant against him. She was so happy that she felt like she might actually explode. They set off together, his arm around her, holding her as they walked along the beach.

To their left, the sun was beginning to sink into the sea and the horizon was a rich pink-purple colour, with banded streaks of orange, crimson and gold. The sea reflected the colour in the sky: it was beautiful. They stopped to admire the scene. After a minute or two, Rose turned to look at him.

"So, how long are you going to stay with me?" she asked.

"Forever," said the Doctor, and kissed her.