The TARDIS had refused to let the Doctor out when he'd landed the sentient time machine on the red surface of Mars, so he'd taken to strolling the corridors in agitation, looking for something to fix or fiddle with, something to occupy his over-active mind, as the TARDIS also refused to move. Turning a corner that had appeared out of nowhere, he almost ran into something highly unexpected: an old woman sitting on a chair that was pushed up against the corridor wall. Her grey hair was loose around her shoulders, and the skin that wasn't hidden by a long floral nightgown was covered in deep wrinkles.

"What?" the Doctor asked in shock, but not solely because of the sudden appearance of the woman on the TARDIS. (He understood, now, why the TARDIS had refused to do anything earlier.) No, it was the identity of the old woman that astonished him most. He hadn't seen her for a long time, and it had apparently been even longer for her, but that didn't stop him from recognising her instantly. She patted the seat of the chair next to her in an obvious invitation to sit, so he did so, still gaping at her.

"How can you be here?" he asked, his voice getting awfully close to the squeaky sound he'd carried over from his fifth body.

"I'm dying, Doctor," she replied, almost nonchalantly. "I thought I already had, but then I woke up here. I figured waiting here for you would be faster than me trying to find you, as I'm not particularly mobile any more, as you may have noticed. I'm glad I'm here, though, to say goodbye properly before I die."

"Oh, Rose," sighed the Doctor, not sure what was going on, exactly, or what to do about it.

"It means I've kept my promise, though," she continued. "I promised you forever. Of course, a lot of that forever was with another version of you, but here I am. My forever's almost up, and I'm going to spend the rest of it with you." Rose's voice was shaky with age, but still firm.

"You were happy, then, over there?" the Doctor asked as he entwined their fingers together as he had once done with extreme regularity. The skin of her hand was wrinkled, and the joints slightly knobby with age, but it still felt familiar.

"I was a bit mad at you at first that you'd left without a real goodbye, among other things, but when I'd slept on it and thought about it a little more logically, I though of how hard that must have been to do at all, and what you'd given up to give to me. We had a fantastic life, surrounded by family. We paid off our shared mortgage ages ago. When he got an odd kind of cancer, we were in our seventies, at least according to the paperwork, but he wasn't going to take it lying down, so he held on stubbornly for almost six years, which was about four years longer than the Torchwood doctors gave him. That was not quite two weeks ago, and I was following him quickly, of old age and heartache. But the universe has other ideas, apparently, and I get to say goodbye to this Doctor, too, before I go," she paused, thinking. "Could you take me to the control room so I can say a proper goodbye to the TARDIS, too?" As thin as the Doctor was, he had no trouble lifting Rose's elderly, frail frame and carrying her to the room they'd once spent hours at a time in, setting her gently on the jump seat and carefully sitting next to her, their hands still tightly clasped together.

"Goodbye, old girl," she said to the air in the general direction of the console. "If you had anything to do with this, then thank you." The Doctor grinned at his brilliant Rose, still deducing and being generally clever in her eighties.

"And even if you didn't," she continued. "Thank you for everything, when I was here before. I missed you almost as much as I missed your Spaceman here. He told me about that particular quirk of Donna's, among other things, " she said, the latter a reply to his raised eyebrow. "I liked it. So I called him that sometimes, to which he usually replied 'Earthgirl'." Rose closed her eyes, smiling.

"Rose?" he asked worriedly.

"'M still here," she murmured. "I don't know how much longer, though. I hurt everywhere, and my head is killin' me." The Doctor didn't know if she remembered saying those words, so long ago, but they started an idea forming in his head.

"Don't, Doctor," Rose interrupted his thoughts as though she knew what he was thinking. "I'm dying, not you. My time is running out, with just enough time for this one last adventure." She was silent for a moment, and then spoke again. "I love you. Always have. When I was with him, it was like another regeneration. I still loved this you, like I loved the leather-wearing, 'lots of planets have a North' version of you, but I loved my current Doctor the most. I'm not sure which Doctor you count as now, but I love you anyway, even if I haven't seen you this young for, oh, fifty years?"

The Doctor made a scoffing sound at being called young, especially by Rose Tyler, human.

"Oh, shut it," she protested weakly. "You know what I mean."

"Rose Tyler," he started. As he spoke, he half expected the cloister bell to start ringing or something, for the sole purpose of interrupting him, as so many thing had in the past. But nothing happened, so he spoke quickly after taking a deep breath. "Rose Tyler, I love you." He hugged her close, and kissed the top of her head softly. She sighed happily and squeezed his hand in hers as tight as she could.

Neither could think of anything more to say, but they were content to sit in each other's company for the unknown but limited time they had left together. The Doctor began to hum quietly, and Rose's attempt to join him turned into a funny breathy cough. He rubbed his free hand up and down her back soothingly, and turned his humming into a soft, untranslated Gallifreyan lullaby. When Rose's coughs subsided, she snuggled as close to him as she could to feel the vibration of his chest on her cheek and the beautifully lyrical language in her ear.

When Rose had promised him forever, this was the situation he had been dreading, the reason that seeing Sarah Jane again had been hard, even as he had enjoyed it, because the inevitability of a scene like this was harder to ignore. But as he held a dying Rose on his lap, knowing she'd lived a long, full life, loved and surrounded by family, it wasn't as terrifying as he'd feared. He'd had to accept the fact that this universe had to do without Rose, as much as he wanted to deny it, so this extra time was more precious than scary. But it didn't stop another part of his very complex brain from trying to do the impossible again and keep her with him, and another part trying to decide where she would liked to be buried.

His trains of thought were stopped momentarily when a series of coughs shook her whole body. He began to rock her back and forth like a small child and sung a little louder, the normally mechanical sounds of the TARDIS becoming the harmony to his melody. A small whimper escaped her lips, and he felt a tear begin to run down his cheek. Other tears followed softly as he couldn't do anything for her pain the way he usually had done when she'd been injured or otherwise hurting. When her breathing became irregular, his voice started to waver, but he kept singing to his precious girl to ease her out of life since he could not prevent her death.

"Don't go, Rose," he pleaded softly, unable to stop himself. "I don't want you to go." Her only response was another shallow, shaky breath and a squeeze of his hand. She wanted so badly to grant him this request, but his most heartfelt wish was one she couldn't grant. She took one more gasping breath before speaking her last words in a voice that was barely a whisper.

"I love you, my Doctor."

"I love you, Rose Tyler," the last of the Time Lords of Gallifrey said one more time as he mourned his beloved.