Author's Note: This is the new version of Recursivity, restructured and revamped. The original first chapter of the previous Recursivity can now be found under the title Ground Zero. Enjoy.

recursive (adj): drawing upon itself; referring back.

Rose had held the Doctor's hand when they had stepped off the zeppelin at the Tyler mansion, and that was rather nice. Made him feel all warm and weird. That would take some getting used to. The warm was strange enough. Experiencing his love for Rose Tyler – intense as it had been as a Time Lord – through the lens of human emotion (Half human, mate) was something else entirely.

She had stood close to him as Jackie went on about being gone for so long, and had insisted to her mum that really, all she wanted was to go back to her flat and have a lie down. Jackie had given the Doctor a very pointed look at that, and the confused look he had given her in return was entirely genuine. He had no idea of what was going to happen next. He hoped it involved more hand-holding. Maybe kissing. That had been nice, too.

So they had taken a taxi to Rose's flat, a little one bedroom close to Torchwood headquarters. The ride over had been silent, and there was no hand holding. The Doctor wondered what he was going to have to do to get her to act like the Rose he'd known only hours ago. Before he was duplicated and given a human life. He pondered it the whole ride there. When they'd arrived, she had taken him inside the building and led him to her floor, but she paused outside the door. Standing in the hall, the chasm between them yawned wide.

"Maybe we should…" He shoved his hands in his pockets, losing his train of thought. "Um."

"Um," she repeated. She rocked on the balls of her feet, avoiding looking at him, but wearing an expression that suggested she wanted to.

It suddenly occurred to him that he wanted to touch her again, and that was why he couldn't think straight. So, carefully, he reached out and touched his fingers to hers. It felt like it took forever for hers to flex and twine with his. She released her held breath.

"Is this alright?" he asked. It had been on the beach. And when they'd gotten off the zeppelin. Was it now?

She looked up at him and nodded. "Yeah. I think –"

"It's easier," he said. "Right? Makes it a bit…"

"Easier." Her lips twitched into the ghost of a smile. He took that as a good sign.

"Maybe we should go in?" (Ah yes! That's what he'd meant to say.)

"Oh! Yeah." She fumbled for her keys and stuck them in the lock. She opened the door to reveal a messy room, a sight that felt achingly familiar.

"Sorry," she said as he stepped in. "Bit of a mess."

He grinned, taking in the blanket tossed over the couch (Had she been sleeping there?), the desk in the corner that was groaning under the weight of books and file folders filled with papers – research, he assumed, to build the Dimension Cannon that brought her to him. The kitchen sink was full of dishes, and there was a sauce pan on one of the burners that looked like it had last been cleaned a month ago. Not like her to be that messy. He wondered for a moment how entrenched she had been in the Cannon project. The thought of her being so dedicated as to not wash the pots and pans made his ego boost a bit. But then he noticed that there were no knick knacks on the shelves, or art on the walls. Mess aside, the flat was devoid of decoration. That made his grin fade a bit.

"Do you remember your old room?" he asked suddenly, turning in a circle to take all of it in. When he faced her again, he looked down at her. "On the – on the TARDIS, I mean."

She smiled, a genuine one this time. "Yeah. Same mess."

"You had stuff on the walls then."

Her smile fell. "People only decorate when they're plannin' to stay."

The gap inched open, and he quickly stepped forward and took her hand, giving it a squeeze. Physical connection reestablished, she squeezed back, and his stomach did a strange twisting thing that made him frown. She frowned back and started to pull her hand away.

"What?"

"No, sorry." He reached for her hand again. He held it between his own, small and fine boned against his long and gangly fingers and large palms. "Sorry," he repeated. "I'm just not used to this half-human business. It makes things…"

She cocked her head. "What?"

"Weird. Not with you!" he added quickly, holding tight to her hand in case she pulled it away again. "Just… weird."

"D'ye wanna talk about it?"

"I suppose we could." He shrugged. "You're human, maybe you can explain a few of the finer details."

She giggled at that. "Having trouble with only one heart?"

He rubbed at the center of his chest. "Keeps doing weird things," he explained. "Flip-floppy and twisty squeezy things." He gave her a puzzled look. "Does yours do that?"

"Depends," she laughed. "When does it do those things?"

"Wellll… When I'm with you, mostly." He caught her eye, and both of their faces split into shy grins. He swung their joined hands, and the gap closed, and for a moment they were as they had been, as if they'd never seen that damned beach, as if Canary Wharf had never happened.

Except this time it was different, because he was no longer himself, but a new self, or something. And this new body could do things that the other one – even with two hearts – could not do. And one of those things was give in to the urge to kiss Rose Tyler.

He stepped in closer, cupping her elbow and bending his head to hers. He tucked her hair behind her ear (he'd always wanted to do that) and her eyes fluttered shut when his knuckles brushed her jaw. He didn't hesitate after that. He leaned down and pressed his lips to her.

She was a little rigid at first, and he didn't blame her. He was right nervous himself. But then her body relaxed, and she rested her hands on his chest, over his one heart, and that was nice, wasn't it? The thing was beating like a fiend. It wouldn't stop, would it? It rather felt like it might. And he no longer had a backup.

Curious, though, that he went on kissing her despite the possibility that he could very well die. His chest was starting to hurt and he felt a bit dizzy, now why was that? Oh yes. No respiratory bypass.

He broke away and sucked in a breath, feeling the air rush in and fill his depleted lungs. She smiled up at him.

"Alright?"

"Yeah," he gasped. "Wizard. Can we do that again?"

Laughter bubbled from her throat. She looked… relieved? Maybe because they'd kissed? Or was it more than that? She'd been so unsure on the beach, about who and what he was or was not. Had the kiss helped?

Well the other one wouldn't have done it, he thought, watching her bite her lip. He'd always loved that. He could admit to himself now that it wasn't just because it was endearing, but because it made him want to bite her lip, too.

That brought about another flip, this time in his gut. This human body was strange. He had an idea what it was about, and without thinking he turned up his nose.

"Would you stop makin' faces?" she snapped. "Or at least tell me why you're makin' 'em?"

"Sorry, I, uh… Flip-flop things again."

"Oh." She smiled. Her hand was still on his chest, and her fingers plucked at the lapels of his jacket.

"Um… hot in here, yeah? D'ye mind if I -?"

She stepped away and shrugged out of her blue jacket, tossing it onto a chair. He grinned and took his off as well, laying it on top of hers. The silence grew and stretched now that they weren't touching. He shoved his hands into his pockets to keep himself from grabbing hold of her and kissing her again. It had worked the first time, but wasn't so sure it would the second.

"Doctor, I –"

"Yeah. Yeah, I –" He rocked up to his toes and back down. "Shall I go?"

She shook her head. "No. Stay." He was glad she neglected to ask him where he would go, because he hadn't thought that far ahead.

"Alright."

Another awkward silence passed, filled with shy glances and hands in pockets.

"D'ye wanna sit down?" she asked suddenly, gesturing toward the couch. He seized the suggestion and rushed toward the sofa, tripping over the coffee table in the process and landing spread eagle amongst the throw pillows. Rose giggled without restraint. He sat up as quickly as he had fallen, embarrassed but grinning. The tension between them bubbled up and over in eruptions of nervous laughter. When it was over, they were still left staring.

Say something, mate. You can't kiss her and expect everything to be banana pancakes after. But he couldn't find the right words, so he just held out his hand.

He knew, at least, that she would always take it.

She sat down next to him, and he put everything he didn't know how to say into his blood and sent it down his arteries toward that single connection between them, willing her to feel it in her palm like a solid object, warm and alive. He wished he could feel her the way the way he used to, when he was a Time Lord – every atom that she was made of, every proton and neutron and spark of electricity that held them together. But he liked the way she felt to him now, no longer subatomic but still intimate, fingerprint to fingerprint. A larger, macro-connection that was somehow… better.

"D'ye remember," she said slowly, "the first words you said to me?"

He smiled. "Course. I said 'run'." He squinted at her. "Why?"

She shook her head, but there was a smile on her face that hadn't been there before. She squeezed his hand, then let loose a ferocious yawn.

"Blimey," she said, "I need to sleep."

The Doctor frowned. "Is that something I do now?"

Rose shrugged. "Probably." She stretched her arms above her head and gave him a sleepy look. "You can, y'know…" Her eyes flicked toward the door that obviously led to her bedroom.

It wasn't that he'd never slept in the same bed as her. On the contrary, it had happened often enough before, after a particularly bad nightmare or a taxing adventure. But he had been a Time Lord then, with complete control over his faculties, and not much need for sleep. Now, with a half-human endocrine system… He couldn't deny, however, the simple fact that he wanted to be as close to her as possible. Forever, if he could.

"Naaaah," he said, and he wondered why. "I can, y'know, sleep out here. If I need sleep. I doubt it."

"Doctor, you slept like a bum on the zeppelin not two hours ago. C'mon."

"Really, Rose, I'm fine out here –"

She looked away, biting her lip. He wished she wouldn't do that. It made it hard to be chivalrous.

"Doctor."

He swallowed. He'd follow her to the end of the universe, if she would always say his name like that.

"Please?"

He swallowed again. "Yeah. Sure."

She pulled him up and towards the door. Same mess inside, but he didn't pay much attention. She was kicking off her shoes and lying down. He pulled off his chucks and slipped in beside her. Without hesitating, she came into his arms, nestling her head on his shoulder and spreading her hand across his chest, like she had done so many times ages ago. She fit against him like a puzzle piece.

"Rose?"

She hummed in reply; she was already half asleep.

"I love you," he whispered. She shifted against him, and he felt her lips on the underside of his jaw. She was asleep before she could reply, but he knew.

He closed his eyes, and for the first time in years, he slept with more than just her memory in his arms.