He really did intend to return the Corvette, he tells himself.

Instead they are heading east, towards the dawning sky. Clara dozes in the passenger seat as he drives, away from the threat of the whispering sea; away from the sonorous clap of the TARDIS cloister bell. Running, like he always has.

She opens her eyes somewhere outside the Sequoia National Park; stretches in her seat. At the gateway of a mighty forest, early morning mist haunts the trunks of pine and fir. She narrows her eyes as they zip past, suspicious. "Did you do something to the engine?"

The tachometer needle is buried at one-sixty. He suspects they are closer to two hundred as a result of his meddling. "I can handle it," he says confidently.

"Don't hurt anyone else," she says, softly.

Their future is fixed, he wants to say. Timelines running parallel, away from those of the earthbound. It's not a question of piloting skills, it's a matter of temporal physics. They won't have an accident. That much he can feel. He takes his foot off the accelerator anyway, bringing them back down to something approaching the actual speed limit. "Are you hungry?"

"Starving. I wouldn't say no to a shower, either."

He pulls up at one of the tourist motels, flashing the psychic paper to gain them a clean but chintzy room. The mismatched patterns of the faded carpet and curtains are an assault on the eye. He finds it depressing; Clara thinks it's quaint.

"Need to get the salt off," she says, running her fingers through stiff hair. "Do we have to pay for hot water?"

The sonic buzzes in response. "Not anymore."

She grins at that. "Come on, then."

He stares at her outstretched hand, nonplussed. She raises an eyebrow and the penny drops, stomach lurching.

"No," he stutters, "It wouldn't-"

"Wouldn't what? Or was last night a one off?" she asks brightly, although he can see fear lurking in her smile, as she waits his response.

Yes, he should say. Something that absolutely, categorically should not have happened. Something that can never happen again.

"No," he growls, taking her hand.

They eat runny eggs with bacon eventually, a very late breakfast. Head north to see the giant sequoias –a mighty tree that is older even than he is. He presses his ear to the bark, to hear any wisdom it has to offer on enduring millennia while the forest grows, dies; changes all around. It has no answer he can fathom, stretching silently to the sun. By evening they are curled around one another in the motel room again, as he commits to memory every inch of her. What's the point of fighting the tide anymore?

They carry on east, taking the Corvette across the salt flats of Death Valley, marvelling at an artist's palette of coloured sands and wind scored rock. "I thought it would be bleak," she says, "but it's beautiful."

"The Universe is full of surprises."

Vegas by nightfall, a room at the Sands. He takes her to hear Sinatra swing. "This last song's for Clara O," announces old blue eyes during the encore (because he owes the Doctor a favour, even if it was to a different face). "At the request of our mutual friend."

He launches into Fly Me to the Moon and she almost manages to hide her tears.

"So, is that out next destination?" she asks, when she has regained her composure.

"Why not?" he replies, as they dance together, in a borrowed white gown and out-of-style tuxedo. "We never did go for those cocktails."

He summons the TARDIS to them the following morning; she materialises somewhat reluctantly. Cross with him, he suspects, for leaving her halfway across the country. She flat our refuses to accommodate the Corvette – with regret he leaves it with Frank – and on they run.

The see wonders. They save civilisations from oppression and tyranny by accident, because it's what they do. They make love on an alien mountain top that dwarves Everest; under the streaming green fire of the northern lights; on one notable occasion in the roof of the Sydney Opera House. The Universe does not end, but he can feel the pressure building; knows catastrophe must come.

"It's almost time, isn't it?" she says softly, at last. His head is resting against her bare shoulder, her hand stroking through his hair, unthinking.

"Yes," he says softly. They've had two months of stolen time. Two centuries would still not be enough. He'll have to delete this bedroom, he thinks. Won't bear looking at it again, remembering her here at his side.

"There's a few things I need to do back on Earth. Ends that need tying up. I need to see my Dad; my Nan."

She was always practical, considerate. "You'll need to do it straight away."

She sighs. "Yes, I thought so." Silence reigns for a while. He listens to her heart beating, counting down. "Doctor… There's something I need you to do for me."

"Anything," he says, and means it. Laws of time be damned, if she asks him to end the whole Universe now he will-

"Bring back my body," she says quietly. "I know what can happen… what technology can do. I won't be a corpse soldier or a cyber slave. Go back and find me. Bury me, or burn me. Whichever seems right to you. And there's a few people who might want a grave to visit. Give me a marker, yeah?"

Of course, she's never as selfish as he is. He nods. "I promise."

He drops her back in town. They go for coffee like they used to, long ago; like this isn't the end of everything.

"It's easier for me," she says, squeezing his fingers across the table, "I'm still going to see you again."

He shakes his head. "Every time I close my eyes," he says heavily, "you'll be with me."

She bites her lip, fighting back her own tears now. "Be good, Doctor. Do amazing things in my name. Not terrible."

"I will," he says, and he hopes he isn't lying.

Her 'phone trills. "That'll be Dad. I better go."

"Yes. Yes, of course." He feels dizzy when he stands, unable to move at first, until she embraces him.

"Don't be afraid," she whispers in his ear as they cling to one another, his own advice from so long ago given back to him. They are drawing stares, all a bit melodramatic for Costa coffee on a shopping Saturday.

"Clara Oswald," he says, for the very last time, "I'll be seeing you."

"Until then, Doctor."

He watches her out of the door as she goes to meet her fate, never looking back. Then he goes to find the TARDIS.

She isn't happy with the landing, readings scrawled across the console screens he has never seen before. He ignores her warning; he has a promise to keep. He hasn't created a paradox, the Universe will just have to endure any warping of time-space their last hurrah has caused. It's the least they deserved.

He opens the door and sees himself, standing frozen over her body. The past Doctor flexes his bloodstained fingers, and then steps forward into the flow of his future. He ignores a sudden mad desire to run and strike himself; to knock him out; relive the whole mad goodbye all over again with her, looping forever-

The other TARDIS is leaving. It is time.

He crosses to her. Eyes closed; she could be sleeping were it not for the wound in her chest, her unnatural stillness. Run clean through. Heart torn asunder.

He bends to pick her up-

And leaps backwards as fire blazes. "No," he gasps. He tried to pour regeneration energy into her the first time around, as her pulse stuttered and failed. It wouldn't take. How can this be happening now?

The golden glow does not engulf her; this is not true regeneration. Instead, the energy settles on her chest, filling the wound. It twinkles for a second longer, a dying ember, and then fades.

He crawls forward, reaching for her with shaking hands. "Clara?"

Her eyelids flutter. She is unconscious but unmistakably, miraculously, impossibly alive. He pulls her into his arms and carries her back into the TARDIS.

His time machine groans and whirrs, taking them immediately into the Vortex with no command from him. He ignores her distress, carrying Clara to the med-bay. Machines click into life as he connects sensors, still disbelieving the evidence of his own eyes that she lives; she breathes. A puckered red scar over her heart, rather than a gaping hole.

How? He asks the computer, over and over, scheduling diagnostics, running scans. How does she live when he felt the life flee her body?

She needs blood, the machines tell him: too little left of her own coursing in her veins. His can be made a match by the wizardry of the sick bay. He does not hesitate, takes a deep breath to steady his trembling and inserts a needle into his own arm. The double-beat of his hearts push red liquid from him to her, down a thin tube.

Clara opens her eyes. "So," she says, a little groggy. "Not dead." She turns her head to find him, sitting vigil at her bedside. "I did wonder if you might have been overreacting."

He shakes his head gravely. "You did die, Clara. It ripped your heart open."

"Then how am I still here?" His mouth twitches as he struggles to find the words. "Don't leave me in suspense, Doctor!"

"Gallifreyan cells," he says slowly, "They triggered a sort of mini-regeneration of the damage. Repaired enough for you to survive."

"From you?"

He puts his head on one side, considering the question. "Ultimately, I suppose, yes."

She frowns. "Doctor, what aren't you telling me?"

"Humans are quite unique, you know, when it comes to making more of you. Most earth mammals just allow a surface interface between maternal bloodstream and placenta, but you… you go the full haemochorial works. Your offspring get direct access, so to speak, pumping you full of hormones. Raising your blood sugar, sending extra nutrients back to help themselves grow. And some cells go the other way of course. Chimeras, your mothers, all of them. Hybrids."

Her eyes widen as she translates this stream of babble. The machines monitoring her vital signs beep, alerting him to her rising pulse, respiration rate, blood pressure. "No," she breathes. "I'm not… I can't be pregnant."

He bites his finger for a moment, considering his response. "Yes," he says eventually, "you are. The stress of your injury triggered the transferred cells in your bloodstream to enter a regenerative state. Not enough of them to change you. But enough to fix you."

"How?" she demands. "How can this have happened?"

He blinks. "I assumed you were familiar with the mechanics-"

"I didn't mean! Of course I know how in broad terms," she corrects. "But you're not human."

"I'm sorry," he says. "It's not unheard of. It's happened before. Not with me!" he adds hastily, before she gets the wrong end of the stick.

She lets out a shaky breath. "And I thought I was dying. No need for caution when you're on that kind of a countdown. Oh, God. When?"

"Eight weeks ago. Any later and the placenta wouldn't have developed enough for cell transfer." He swallows. "The beach, I think."

"I hadn't forgotten." The smallest of smiles tugs at the corners of her mouth, freighted by the memory. Her pale fingers inch across the covers, find his worrying the hem of her blanket. She gives them a gentle squeeze. "What do we do now?"

"I don't know," he lies, "Whatever we want, I suppose." As if their decision hasn't been prophesised, millennia ago, on Gallifrey.

Is that what you ran from, Doctor? The coming of the hybrid? He should have listened to the call of the Universe, instead of allowing his own misery and fear to consume him. And then she'd be dead, another part of him reminds. She lives because he saw her die. And he doesn't think there's a version of reality that exists where the Doctor can let Clara Oswald die without a fight. If there is, he's glad it isn't this one.

"What do you want?" she asks.

Very gently he lets go of her fingers and reaches across, his hand hovering millimetres over her stomach. She nods her permission, and he spreads his fingers across her lower abdomen with uttermost delicacy; closes his eyes. A thousand potential futures map on to his eyelids, charcoal sketches in shades of grey. One, outlined white hot. The weight of his child in his arms again; sleepless nights; unmitigated love. The Doctor and Clara Oswald, in the TARDIS.

"This," he says.

Prophecies be damned.