"Clara," the Doctor hissed urgently, taking her hand and pulling her away from the dusty flow of the moon market into a curtained kiosk. The blue-skinned proprietor took one look at his wares, one look at the Doctor's expression, and fled for his life. "I don't know who he is," the Doctor continued. "There are a few people he could be, all of them bad. But he isn't me. Whatever he has said, whatever he has told you, he isn't me. He cannot be me."

Her heart slowing from her initial startled response, Clara smiled fondly at the bowtie-bedecked face she had never expected to see again. Running into previous versions of the Time Lord had happened before, of course. It wasn't supposed to happen, he'd told her, so naturally it happened to him all the time. But this was uncharted territory.

The Doctor had once admitted to her that he'd been terrified of what should have been his final regeneration, fighting the deadly radiation for long enough to rage against the dying light in his penultimate body. Later, his second chances utterly spent, he'd made peace with death; even welcomed it, his long companion, come to stay at last. Up until the moment on Trenzalore when the Time Lords refilled their dying renegade with living fire, he'd thought he'd never have another new self - and certainly not this one, who was standing at the threshold and rolling his eyes.

"Doctor," she said fondly, patting his youthful hand. "It's really okay. He's you. Or, you're him, however that works."

The Doctor stepped into her, stooping so his face was inches from hers, jaw working as his expression flickered between gentle and thunderous. She'd forgotten he did that. She'd forgotten how the boisterous young man sometimes dropped away, exposing the ancient anger and despair beneath. She'd forgotten that he could be terrifying.

"Clara," the Doctor said quietly. "That is impossible. Are you in trouble? Are you his prisoner? Is he making you say those things? Just tell me, and I'll get you out if this, I promise." He flexed his fingers at his side, then violently spun away and shoved his future self against a tall glass case, which tilted precariously as the men grappled.

"Who are you?," the younger man hissed, twisting the lapels of the elder's dark coat. "The Master? The Valeyard?"

"Oh, you are an idiot," the Doctor said tiredly, wincing as he rubbed the back of his gray head.

"Doctor!" Clara cried, pulling him off himself. "Seriously," she said, pushing him behind her and directing a scathing look at his other self. "Can't you get along with anyone?"

The Doctor boggled at her from beneath his expressive eyebrows. "Why are you cross with me? He's the one ignoring his own senses and bashing people into walls."

"Because, shut up," Clara said. She stabbed a finger at him. "Because he's confused, and at a vulnerable point in his timeline. Because you're amused by this. Because I'm more comfortable yelling at you."

"She's bossy, I've found," the young man said conversationally.

"You have no idea," the elder shot back, straightening his rumpled coat.

The Doctor sighed, pacing in a small circle before pressing the heels of his hands to his eyes. "Bow ties no longer cool, I take it?"

"No."

"Scottish?"

"I blame Amy. And Jamie."

"Gray hair again? Really?"

"Oh, believe me, bow tie boy, this is a vast improvement from where you leave off," the Doctor said with a smirk.

"What did you do?" the other asked, his temper abruptly flaring again. "What laws of the universe did you break, what part of your soul did you sell, just to regenerate again? And why, oh why, would you want to?"

"Me?" the Doctor asked innocently. "I didn't do anything."

"Don't." The Doctor snapped. "Just, don't. I'm not in the mood to, to parse pronouns." The two Doctors glared at one another across a hostile silence.

"Sooo," Clara drawled, breaking in, glancing between them both. "You recognize you now?"

"I suppose so," the younger Doctor admitted. He tapped the side of his head. "The Tardis certainly does. And I believe you."

"I'm there when it happens," Clara said gently. "I watch you change. And I know it seems impossible to you, but there really is an explanation ... which I suppose I can't say?" she trailed off, directing the last to the Doctor who was chewing the side of his thumb and deliberately not looking at his earlier self.

"No," he answered, glancing apologetically at her. "I don't remember this, but best not risk it. Not spoilers like that. Although I can tell me this." The Doctor glared over at himself, and raised two fingers. "Impossible new regeneration cycle, explained in two words: Clara. Oswald."

The Doctor had been squinting skeptically at his future self, but at the words his face smoothed into solemnity, cracking through the youthful facade. "Okay," he said, bemused. "Impossible girl, impossible things."

"My impossible girl," the Doctor growled.

Clara blushed. "When are you?" she asked the earlier version of her best friend, tilting her head at him. "How long have you been traveling with me?"

"A couple of weeks," he said with a shrug. "I take it that it's been longer for you? Which, I must say, is a welcome bit of surprising news."

"A while longer," she murmured vaguely, brushing back some of his floppy hair to study his face. "You really are at a vulnerable place in your timeline. And I'm still just a puzzle."

"Well. No. Not 'just.'" The Doctor said, clasping and unclasping his hands. "You're interesting, and funny, and quite marvelous. And a puzzle." Clara laughed. "Do I ever solve you?" the Doctor asked, his voice warm. His successor snorted.

"Well. You like think you do," Clara laughed. The Doctor wrapped his arms around her and kissed the top of her head. "See, that isn't so hard," Clara said, smiling into his neck but looking beyond him. The Doctor not currently hugging Clara threw up his hands, then crossed his arms and glared at them.

"He's a grump," the Doctor complained, glaring back.

"You can be a bit prickly," Clara sighed. "You're about to have a bad run of years that will break your hearts again, and so you pretend not to care." Both Doctors frowned at that, the expression eerily identical on two very different faces. "But I know better," she continued.

The Doctor smiled down at her. "I don't suppose I can talk you into coming with me?" he asked. He regretted the question when his future paled.

"You can always talk me into coming with you," Clara said, giving him a hug through his tweed coat before stepping away, reaching back to take the other's long-fingered hand. "So you'd better go find me and ask."

The Doctor gave her a grin and a wink. "You are extraordinary, Clara Oswald. Mind if I have a private word with myself?"

Clara laughed. "I'll just go have a look around, yeah?" she murmured to her companion, who nodded wordlessly. "Better hurry, before someone arrives to arrest you for robbing this shop." The young man laughed and gallantly swept open the tent flap for her.

Once Clara had slipped away under his arm, the smile dropped from the Doctor's face, and he studied his impossible successor. The little moon spun beneath their feet and the particles of the expanding universe raced apart ever faster around them as he closed his eyes and sank into the shimmering timelines. The twisting shards of his infinite might-yet-bes sparked dangerously against the hardened stream of his future's fixed past, threatening paradoxes and destiny loops which were held at bay only by the multichronic will of a Time Lord. Just one Gallifreyan here, in truth, but for a lonely heartsbeat, he could pretend that the returning echo of his own voice was the lost song of his dead people.

"I know why I didn't recognize you," the younger Doctor murmured, opening his eyes wearily.

"Hope. I find that harder to fathom than the regeneration. Where does the hope come from?"

The future Doctor shrugged fluidly, his gaze lingering on where Clara had last stood. "Spoilers," he murmured absently.

"Who is she?" The Doctor asked, giving himself a calculating look.

The Doctor glared at his younger self and stepped toward him, angry for the first time in the encounter. "No," he said, shaking him by a fistful of his tweed coat. "She is not a puzzle. She is important. She is more important than you can fathom. Important to me." The Doctor released himself and gave him a sharky grin before reaching out and straightening his bow tie, the once-expert gesture slightly out of practice.

The younger Doctor shook his head, his face dark with pain. "I promised myself I wouldn't do this again," he whispered harshly. "I swore I wouldn't. Did I forget? How could I forget that this ..." he waved his hand in the air, not able to speak the word, "will always break my hearts in the end?"

"I know. She's worth it," the elder answered fervently.

"She'd better be," the Doctor sighed. He walked away in frustrated agitation, unwilling to face the self-pity in the pale depths of his own eyes. The muscles rippled across his jaw, then he slumped and turned back with a sigh. The other Doctor just smiled faintly.

One of them offered a handshake to himself. "I'm not sure I'm glad to see you," he said.

"Likewise," the other answered dryly.

"Take care of her. And yourself, while you're at it."

"And you," the Doctor said, gripping his hand. "Doctor."

"Doctor," he said.

The old man who looked young inclined his head to the ancient man who felt new, before stuffing his hands in his pockets as he turned away, knowing the encounter with his future would drift from his memory until the timelines synced. He smiled at Clara, who was hovering worriedly just around the corner, and disappeared into the crowd. Behind him, the Doctor shook his head as the old memory resettled in his mind, running his hands through his silver hair and down his face as he breathed through the echo of his own despair.

"Are you okay?" Clara asked, peering into the tent.

The Doctor smiled at her, a little bleakly, then shrugged a bit guiltily at the mess in the kiosk before following her into the light. They slipped into the crowd just ahead of the arrival of the blue-skinned shop owner, who had a flustered constable in tow.

"Not really," he said as they walked, his voice low and nearly lost in the hum of the market. "I remember this now. I couldn't believe any of it. Regeneration. Second chances. You, still with me. I'd forgotten how I was when I first met you. I looked younger. I was younger. But I felt older. Or perhaps just more broken." He shook himself, embarrassed by his honesty. "You didn't go far," he continued, changing the subject.

"Never," Clara answered softly.

"And you?" the Doctor asked. "Are you okay?"

"That was odd," Clara admitted. "I remember looking at that face, and it seemed so inscrutable. You were good at hiding from me, then, but now I could see ..." she trailed off. "You haven't looked at me like that in ages."

"Like how?" the Doctor asked, knowing the answer.

"Like you were seeing ghosts. Like I was a mystery."

The Doctor gave her a crooked grin. "You're still a mystery. For example, I have no idea why you put up with me."

"Some questions simply can't be answered," she teased, feigning long-suffering as she looped her arm in his. He smiled down at her as she dashed off to pet the silky scales of some mer-kittens. In the distance, he felt his younger self leave, richer than he knew because he still had so many of Clara's precious days to spend.

"Treasure each of them, Doctor," he murmured, then shook himself and followed Clara's laughter to their next adventure.

Tiltle from Thoreau: "The meeting of two eternities, the past and future….is precisely the present moment." Thanks to the wonderful Kim for the beta.