Set after School Reunion.
Part Two:
Looking at the Doctor, Sarah Jane and K-9, Rose couldn't help but feel jealousy running within her heart. The Doctor may have made a promise to never leave her, but here he was, chatting happily with Sarah Jane and the metal dog, to whom he'd also promised he'd never leave them. So much for keeping his promises.
She took the opportunity to confront the Doctor as they left the coffee shop, taking advantage of the fact Mickey, Sarah Jane and the dog all left before they did.
"I've been to the year five billion, right, but this? Now this is really seeing the future. You just leave us behind. Is that what you're going to do to me?" Pain, anger and jealousy all fought within her, making her lose her temper faster than she ever believed was possible.
The Doctor's voice was strained when he replied, and she could sense pain radiating from him. "No. Not to you."
"But Sarah Jane?" She insisted, "You were that close to her once, and now you never even mention her. Why not?"
He stopped in his place, looking at her intently. His brown eyes seemed darker than she'd ever seen them. His pain was written all over him as he spoke again. "I don't age. I regenerate. But humans decay. You wither and you die. Imagine watching that happen to someone you…"
Her look turned softer. "What, Doctor?"
"You can spend the rest of your life with me," His voice was quiet and filled with pain, begging her to understand. "But I can't spend the rest of mine with you. I have to live on. Alone. That's the curse of the Time Lords."
The Krillitane's attack cut their conversation off, but neither Rose nor the Doctor forgot about it. In the end of the day, once Mickey had retired to sleep and Rose hinted she was about to do the same, the Doctor stopped her, looking at the console intently.
"Rose." His voice was quiet and filled with too many emotions for her to name them all. She stopped and turned to look at him, hoping he was going to say something about that conversation. "You should know… when I said I won't do that to you, I meant it."
"Didn't you mean it when you said that to everyone else?" She asked softly, using the softness of her voice to try and hide her pain and fear. He wasn't fooled by it; he could sense her emotions through any disguise.
He surprised her when he shook his head and said, "I didn't say it to everyone else."
She blinked in surprise. "What?"
He finally looked up at her, his brown eyes once again dark with emotion. "I didn't say it to others," He said simply. "Those who travel with me… who used to travel with me," He corrected, "They always knew it's not going to last forever. Traveling with me was always temporary."
"Sarah Jane didn't," She reminded him quietly.
He nodded slightly. "That was my mistake. I should have said goodbye before I left." He looked away again, his fingers drumming over the console in front of him. "I never know when and how it's going to end, but I always know it will. It has to. Some leave, some get hurt…" She could practically hear his self-loathing in his voice. "Some get left behind. I never promise it'll be forever, because it can't be, and I know it."
Hesitantly, not entirely sure she wanted to know the answer, she stepped closer to him and asked, "Then why promise me this?"
He looked up at her, surprise in his eyes. "Because you're Rose Tyler," He said, his tone indicating it was obvious. She frowned, having no idea what he was talking about. He sighed quietly. "Remember what I told you when we sat on the grass in New Earth?"
Still frowning, she nodded. "Yeah."
"I told you I wouldn't have been here if it weren't for you." She nodded briefly, telling him she remembered. "I meant it. How many times did you save me? I wouldn't have been the man I am today if it weren't for everything you've done for me. Everything you've changed in me."
"So… What? It's about gratitude?" She asked, her voice shaking slightly. Gratitude was nice, but deep down, that's not what she'd hoped for. Not from him.
He shook his head. "Of course not," He said dismissively. He hesitated before he continued, his eyes meeting hers. "I can't imagine doing this without you, Rose," He admitted simply, causing her heart to skip a beat. "And when I told you I'd never leave you… I meant it. I know meeting Sarah Jane made you doubt it, but my promise hasn't changed. If I ever end up leaving you behind, I hope you know I'll come back, no matter how hard it would be or how long it would take."
Looking at him silently, she made the few steps between them and gently took one of his hands with hers. How could she ever doubt him? She knew he'd never do that to her, deep down, in that place in her heart where she knew the Doctor better than anybody else. He promised her. She knew it.
"It's you and me, yeah?" She asked, smiling.
He smiled back at her. "It's you and me," He confirmed, holding her hand tightly. "Yeah."