AN: A sort-of sequel to Profit & Loss but not totally conditional to the other story. We start with a difficult conversation. Beginnings aren't always easy but they are hopeful. A big thank you to beta T'Kirr for the edits.

"The Doctor, the man who keeps running, never looking back because he dare not, out of shame."

Being human was all about learning. In that way, it wasn't so different from being Time Lord. There was, however, a distinct emphasis on hindsight. The Doctor had always been one to look ahead - on to the next adventure, the next companion, the next life. But now, finding himself with precious little time in the life ahead, his thoughts drifted to the past more than ever before.

Being human was also about empathy. Not that he didn't always have compassion for his fellow travelers before. Sharing their limitations, weaknesses, and feelings, though, put a whole new perspective on humanity. For the first time, the Doctor saw life from the other side of the TARDIS doors. He was the one shut out and left behind, while the immortal Time Lord moved on to the next life without looking back.

"I've been thinking about Davros," he told her on their last day in Barcelona, out of the blue, like he was commenting on the weather. "Some of the things he said."

They were sitting on the mosaic serpentine bench of the main terrace overlooking Park Güell, snacking on samosas and patatas bravas which Rose insisted on calling 'Spanish chips' instead of their proper name. It was a beautiful, lazy day and she couldn't imagine what might inspire such dark thoughts.

"I think that's the last - " Rose struggled for a vulgar enough term for their shared enemy and, finding none, continued anyway. "...person you should be thinking about."

"Maybe not," he disagreed, regarding her seriously. "Enemies have a way of knowing you - predicting you - sometimes even more than friends. That's what he wanted to show me... him," the Doctor faltered for a moment, as he often did these days when he was unsure of how to refer to the joint past with his separated self. "Lay all the mistakes and shortcomings out plainly for all to see. He wanted to break me by showing me what I really am, called it his final victory. And it would be, Rose, if I didn't overcome it. If I don't learn from it."

Rose tried to listen objectively but couldn't help fixating on something that didn't add up in his story. "But... how could you know that? You weren't there when he said that."

He blinked, momentarily taken aback, and despite the serious topic fought the urge to grin at how Rose continued to impress him with her skills of observation.

"Well," he began, drawing out the word very slowly to take up time, which Rose took as a foreboding sign for the upcoming explanation. "We had the TARDIS then and between the two of us she worked out a sort of feedback loop. A bit like a backwards ripple - but more like a sideways ripple, really - and any memories of our divergent time that day while the TARDIS was still present were shared."

She ruminated over his words and began to wonder if that meant the original Doctor had vicarious memories of their first kiss too, when the TARDIS was still there on the beach. Watching him walk away and knowing the Time Lord might be out there right now carrying that with him just made things more confusing. She wasn't sure how to feel about it and was starting to wish they'd never set out on this conversation.

The Doctor continued, bringing the focus back on his original intent. "I've been thinking about Donna too. And about what you said, looking for a purpose outside of the two of us."

He looked at her with an open vulnerability that begged the importance of her understanding. Sharing decisions with her was something Rose was still adjusting to. During her time traveling in the TARDIS he often asked her where she wanted to go but ultimately their next step was always in the hands of the designated driver. Having a part in his destiny now seemed a momentous responsibility. It reminded her of what her mother always told her a relationship should be, a thought that made Rose suddenly feel very 'grown up.'

"Okay," she said resolutely. She did believe finding his own identity was drastically important and was prepared to support him wherever that endeavor took them. "What do you want to do?"

He smiled at her intuitive open-mindedness but it faded a bit when he remembered what he was about to tell her. "First, there are some things you need to understand. About a human-Time Lord biological metacrisis."

If they had to have this conversation in public, Rose was glad it was in a foreign country where the people around them hopefully didn't speak English, or at least not as a first language. It was a late, mid-week morning so the terrace was less crowded than usual but the park was still a popular destination. They were far from alone, tourists and locals alike milling about all around them.

The Doctor seemed to anticipate her concern because he stood up and nodded toward the grand stairs leading down to the entrance and the plaza below. Rose followed his lead, walking next to him at a leisurely pace.

"I know the basics," she reminded him calmly. "You're here after all. So tell me what I don't know."

He paled at the thought of having to start in the middle. Explication was best tackled from the beginning. He struggled for a moment as they ambled on, finding the words that intersected brevity with layman's terms. Once the connection came to him, it seemed obvious. The spark of recognition manifested as a bounce in his step when he turned to face her, walking backwards with hands in his pockets and making it look irritatingly easy.

"You remember the nanogenes?" he queried animatedly. "You know, barrage balloons, gas masks, Captain Jack, 'are you my mummy?'" his voice rose in pitch at the last in a spot-on imitation.

She nodded and smirked. "Big Ben," she added with a twinkle of mischief.

In his new clothes, Rose thought he looked rather dashing. It was a bit distracting, if she were to be honest. She hadn't been able to convince him too far away from the three piece suit but at least he'd left off the jacket for the warmer climate today. With all the carefree exploring of the past couple days, it was easy to get caught up in his energy.

After swiping a scrap of psychic paper from Torchwood, effectively restoring the Doctor to nomadic greatness, they had left London without even bothering to pack, picking up clothes and supplies along the way. In some ways, even as they sauntered along the terrace, it felt like this was the first time they'd come to a stop.

He smiled briefly but it faded again quickly as he turned and fell into step beside her. "The regeneration energy that became, well, 'me' needed guidance to finish the form. Just like the nanogenes. Needed to learn. It learned from Donna. That's why I'm part human."

"Is that a problem?" she asked thoughtfully.

Blimey, was that a loaded question. Was being human a problem? Problematic, surely. One heart, inferior biology, pathetic immunity and slow decay. But he was pretty sure that wasn't really the gist of what she was asking.

"Not for me," the Doctor settled on the half-truth. "But the process backfired, creating a two-way biological metacrisis."

"Doctor-Donna," she recalled.

He nodded grimly. "A Time Lord consciousness in a fully human body. Amazing, but unstable. Dangerous. She couldn't maintain it for long. Her mind would burn."

Rose froze in place. Tears sprung to her eyes and she clasped a hand over her mouth. "So she's -"

"No," he jumped in quickly, reaching a hand out to rub her arm reassuringly. "The plan was to take her memories. But - I mean all of them. Everything from the moment she appeared on the TARDIS. She's alive, I'm sure. Safe. But Donna, the one I knew, the woman who saved all of reality... she's gone."

The weight of this truth crashed down on Rose powerfully. She agonized for Donna, losing not just the recollection of adventures but a piece of herself. An important piece, the brave little part of everyone the Doctor touched that he made better. And she mourned for the Time Lord, having to be the one to take it away from her.

"But he said he'd have Donna with him," she remembered. "That he wouldn't be alone."

"Rule number one," the Doctor muttered sourly.

Rose furrowed her brows in confusion, incredulous at the completely inappropriate response. "Don't wander off?" she submitted for confirmation.

"Ah," he realized. "I did tell you that, didn't I?" He was surprised she remembered given how many times she broke that particular order. "That is rule number one for you. For anyone who traveled with me. But in general, it's 'rule number one: the Doctor lies.'"

He turned to meet her eyes and saw a bleak sadness come over them before her gaze flitted down to the plaza below. "You too, then," she presumed darkly.

The Doctor heaved a tired sigh born of a thousand bitter memories that weren't really his to regret. "Suffice to say it's a habit I'm trying to break."

She nodded, in relief and affirmation both. "I think I can help with that. If you'll let me."

He smiled then, an upturn of lips that spoke more of gratitude than happiness. "I hope for that. I know it's too much to ask - "

"It's not," she blurted suddenly, cutting him off. With her own small smile she found his hand and threaded their fingers together in an unspoken gesture of comfort.

He stared at their joined hands for a beat before tugging her along to follow him down the stone staircase. The Doctor stayed quiet for a long moment then, pulling together coherency and courage to keep going.

"I want - " he started haltingly. "I think I need to fix it. The things that went wrong this time around. The events leading up to the metacrisis were predetermined somehow. A causal loop. I'm still me, and I can't help but think there's a reason for that. It must be the human part." He chuckled dryly and looked up with a teasing spark lighting brown eyes. "You lot are so obsessed with finding meaning in everything."

Rose sniggered despite herself. Yup, he was still himself all right, insulting other species to cover his own nervousness. Even when he was now included in one of these species.

"How?" she asked hesitantly as they reached the bottom of the stairs. She didn't want to rain on his parade but she couldn't see how he was going to mend things that happened in the other universe when they were stuck here.

He coaxed her to sit with him on the steps next to the Dragon Fountain and pulled something from his pocket, presenting it on his palm. Rose recognized the chunk of coral from the TARDIS, the other Doctor's last gift to them. She was surprised at first that he'd brought it with them but then she figured he wouldn't want to let it out of his sight. Instinctively, she reached out her hand to touch it and something made her startle and gasp, a free hand flying to her chest.

The Doctor watched her intently. "Can you - " No, it was impossible. Ridiculous. He shouldn't even voice it. "Can you feel it?"

"You mean the hum?" she wondered breathlessly. "Yeah, a little bit. But..." That wasn't what had made her jump.

Amazing, fantastically brilliant Rose Tyler, how could he have ever doubted? The words BAD WOLF flashed across his brain. Rose had to give up the Vortex, but it seemed the TARDIS was reluctant to give up Rose. Some part of his two loves were still connected.

She shocked him even more when she fingered under her shirt collar for a silver chain, tugging until her glowing TARDIS key came into view. He caught it reverently and beamed at her like Tony on Christmas morning, consumed by awe and wonder that the presents before him were somehow magically his.

"Rose," he venerated her name, just a whisper overcome with emotion.

In the next moment she was swept up in the Doctor's crushing embrace. The angle was awkward on the stairs but she accepted his hug happily, stroking his shoulders as he lingered, nearly trembling with jubilance. Rose savored his warmth and she almost swore the scent of stardust was a little stronger. He squeezed her tightly once more and jumped away just as quickly as he'd moved in.

"You know what this means?" he chirped excitedly.

She laughed brightly at his enthusiasm but shook her head indicating she'd no idea.

"Your key is the key, Rose. Look." He pocketed the coral and held up the key near her face so she could see the golden shimmer. It was warm, almost buzzing, in his grasp. "It's got Vortex energy stored inside. The new TARDIS - our TARDIS - can assimilate the energy from both sides of the Void. She'll be able to travel in both universes."

"But we can't get back," she pointed out sadly, gently taking the key and tucking it back in her shirt. "You said it was impossible."

He shrugged, nonplussed. "It is impossible. Doesn't mean we shouldn't try."

Rose snorted derisively. "Like you tried to get back to me."

His face fell instantly. "I did try," he lamented, pain shining darkly in his eyes. "Rose, how could you think..."

She looked away, suddenly feeling childish. "I'm sorry, I shouldn't have... It's just, you never said."

"I tried everything," he confessed quietly. "After Donna turned me down the first time around, I traveled everywhere I could think of looking for an answer. There was nothing. Every wise man, library, infodisk, and data matrix was a dead end."

The Doctor smoothed his hand across her cheek until she looked back at him. "You were the one that found a way," he smiled wistfully.

"But the walls were breaking down, then," she protested stubbornly. "The Dimension Cannon doesn't work anymore."

"There's no guarantee," he allowed. "All I'm asking is if you'd be willing to give it a go."

"You want to go back," she said, part question part statement. Her voice was even, withholding opinion of his answer.

"Theoretically, there's a small chance we may be able to preserve Donna's memories. At least up until the metacrisis. It will take a lot of research. And luck. And practice of skills I'm not even sure I have anymore - " he took a deep breath and scrubbed a hand over his face in exasperation.

"I get it," Rose assured him, gathering his hands up the way he always did when she was uncertain. "You want to help her. That's good, I think. Let's try."

"Yeah?"

She smiled widely. "Yeah."

He grinned broadly in kind. "Because, Rose, if anyone could do it, it'd be us."

Rose hummed happily and looked out across the square, at peace with their idealistic plans for the future. At least this time they were together. That doubled their chances of pulling off the impossible.

"So," she began conversationally. "Donna turned you down?"