She was his constant, she was always there. No matter what happened, he and Rose were together. The Bad Wolf and The Oncoming Storm. In the TARDIS. That's how he saw it. It allowed him to do such crazy things – to take those risks – because at the end of the day, he always found his way back to her. Or sometimes the other way around.

He thought it would always be this way, but the universe appeared to have other ideas, and recently, it seemed harder for them to stay together.

Rose leaned against the console in the control room. She was thinking about their last trip – to a spaceship in the 51st century – where they met those clockwork creatures, where the crew had been cut up and used to repair the ship. Where they met Reinette. Where the Doctor left her.

She sighed as the thoughts buzzed round her head. Her mind was stuck on a loop and there didn't seem to be a way out.

Why did he leave her?

At the sound of footsteps she tried to compose herself. At some point, tears had escaped her, and she hastened to remove them – she couldn't cry now.

The Doctor bounced up the stairs and immediately started messing with the controls.

"So, where to next?!" He asked excitedly. After their last adventure he had been unusually quiet, but now he seemed to want to move on as fast as possible.

"The Medusa Cascade? Mellissa Majoria? Oh, I know! The Palace of the Bronze Empress of Delta One! Brilliant! Year-long festivals… Imagine! Or… Barcelona?! We never did do that, did we?" He spun round, grinning at Rose, but she was too pre-occupied with her own thoughts.

Concerned, the Doctor moved towards her.

"Rose?" She usually listened to everything he said, responded immediately to any question, but right now her eyes were vacant, mind far away.

"Rose?" He asked again, a note of panic creeping into his voice. He stood directly in front of her now, putting a hand on her arm. At his touch she came back to the present, although her eyes were still avoiding him.

"Where's Mickey?" She asked.

"Just…" her question threw him, "looking around the TARDIS, he's fine…" he said dismissively, still distracted. "Are you okay?" he asked, dark eyes frowning.

"Yeah" she said quietly with a weak attempt at a smile.

She was lying to him, that much he knew, but as to what about, he was clueless. He was going to find out though. Why was she avoiding his gaze?

He opened his mouth to speak, but she quickly stopped him.

"I'm fine" she said, brushing his hand off her arm. She needed answers, not sympathy. She tried to walk off, hoping he would drop it, but he grabbed her arm and turned her round to face him.

No," he said, firmly, "you're not. Tell me what's wrong," he urged her.

She couldn't escape those eyes – their intensity, their fire. She didn't want to bring it up, but he'd never let it go now and truth be told… it was eating away at her.

But no. It would only hurt him.

"It doesn't matter" She looked at the floor.

"Hey," he said gently, "you always matter." He said this so seriously, was so full of conviction that she almost believed him.

Almost.

Rose sighed. She was going to have to say it.

"Yeah but… that's just it, isn't it Doctor?" she said softly. He was frowning, not sure what she was getting at. "I don't matter." She said simply.

He opened his mouth to protest – always ready to defend her, even from herself – but she carried on.

"I mean, I might… sometimes… until something – someone – more important comes along and…" She tried to keep herself together, "And then I just get… forgotten."

Rose felt him freeze in place and her eyes stayed on the ground, waiting for his reaction, but none came. One glance at his face made her want to retract the whole thing. He looked like… like a broken man. But why?

"I could never forget you." He whispered sadly.

At this Rose felt an anger so intense she couldn't control it. How could he say that after what he had just done?! He forgot her all the time!

"You left me!" She shouted instantly.

She could feel hot tears falling freely now, all her pain and fear and confusion thrown into those three words.

She tried to calm down.

"I know I'm not the most important thing, that… that I'm not… I'm not…" She couldn't finish, couldn't even breathe. She looked up into those burning eyes and suddenly she felt very small. An insignificant girl, nothing compared to this great wise man who knew so much.

She realised the truth.

"I'm nothing compared to you." Rose whispered, more to herself than anyone else before breaking into sobs. So much for staying strong.

"Oh Rose," The Doctor sighed, pulling her close to him. He couldn't bear to see her in such a state, and he had caused it! How had he been so reckless? Rose couldn't ever think of herself like that – he wouldn't allow it. She was brilliant and beautiful and shining.

He stroked her hair, trying to soothe her as she cried. He needed her to stop before both of his hearts ripped in two.

After a while she pulled back. "Sorry." She said in a small voice.

The sight of her made him want to scream. Never had she looked more like a lost girl, and now she was apologising for it! He had to fix this – it was all his fault.

Maybe now was the time to tell her.

"Rose, look at me." She didn't move. "Look at me." He said through gritted teeth. His anger at himself was barely contained; she looked up at the change in his voice.

"Don't you ever, ever think… like that" he couldn't bring himself to repeat what she had said about herself.

"You a-" he cut himself off as he swallowed the lump in his throat. "You are so important to me, I… I don't know what I'd do without you." He paused.

"You saved me."

Rose didn't really know what to think now. She wanted to believe him, she truly did, but it still didn't make sense.

"But…" She frowned, "you ran off. You went back… for her." She whispered.

Sarah-Jane had told her, said that it was worth it - that he was worth a broken heart - but Rose wasn't too sure if that was all that would break.

The Doctor sighed. So that's what this was about, not just that he left her, but that he left her for someone else. Or that's how Rose saw it.

But that's not it at all.

"No," was all he could manage. She looked at him for further explanation, but he couldn't give it to her. If anyone could leave him speechless, it was Rose.

"I know," he sighed "I know that it looks like I chose her over you, but it's not like that." Once he started, it was like opening a floodgate and the words came faster as he tried desperately to make her understand. "Those things would've changed the whole of history if I hadn't stopped them – you know that. One tiny little thing different and it all goes wrong; time is rewritten and everything changes like that-" He snapped his fingers to better illustrate his point.

"Children never born, meetings never made," he paused, "life never loved…"

That was the best he could give her.

Their eyes locked as a deeper message was conveyed and understanding seemed to flicker across Rose's face. He dropped his eyes, trying to ignore the pain of what he was about to say.

"As… hard" – nowhere near a strong enough word – "as it would be for me to lose you now… I'd rather that than lose it all… than have you just fade away…" His breathing rate increased as it always did when he was thinking of something unspeakable. "Erased…" he whispered.

He gripped Rose's arms as his mind explored the possibility of such a terrible thing. He couldn't comprehend it.

Rose was stunned.

The Doctor was the bravest man she had ever met, and even when he was scared, he always found some measure of control – a solution – but not now. He looked distraught, his eyes glazed over and mouth slightly open, lost in some private hell with no way out.

It terrified her.

A single tear rolled slowly down his cheek, but he didn't seem to notice, eyes impossibly dark and miles away. He couldn't be like this, this was wrong. She had to fix him.

"Hey," Rose said gently. Slowly, she brought her hand up to his face and wiped the tear away, keeping her hand there. The Doctor's eyes came back to her, desperately searching her face. Rose wasn't sure exactly what he had been thinking of, but she could take a pretty good guess.

"I'm here, look, I'm fine. You did the right thing – you're right, I don't want the past to change either."

He still looked wrong.

"I'm sorry I left you," he whispered shamefully. After all he never really considered how Rose would feel whilst he went off to save the day. He knew he would come back, but what about her? All she could do was sit and wait.

Rose smiled. "It's okay, like you said; it was the only way to fix everything." He didn't look convinced. "Really, Doctor. And anyway, it all worked out for the best." She smiled again.

"Yeah," he agreed quietly with a small smile. The Doctor could see that Rose was ready to move on and he tried to do the same for her, after all, he hated it when she worried for him – he wanted her to be happy.

He looked down at his Rose, thinking how the small smile on her lips didn't quite hide the concern in her eyes. Her hand was still resting on his cheek, trying to soothe his pain. Would she ever stop saving him?

The Doctor pulled Rose into a tight hug, lifting her off the ground and into his arms. She hugged him back, her arms wrapping like a vice around his neck. They needed each other so much, but the unpredictability of their lifestyle made most words too painful.

Words weren't enough anyway.

He just had to ask her one more thing.

"So…" he tried to pull back to look at her face, but she wouldn't let him, "you still going to stay with me?" he asked.

She didn't miss a beat, "Forever." Rose whispered, fiercely.

He could hear the smile in her voice as she pressed her face into his shoulder.

He held her closer, tighter, and for one beautiful moment, he allowed himself to believe it too.