Past: Hand Brushing Hand

He had always followed her if he could; there had never been any doubt about it. The only thing that had ever remained in any sort of doubt in his mind was whether she would follow him back.

She was too electric; too much like lightning that danced here and there, striking without warning before disappearing again. His earthy reality hadn't been able to comprehend hers. Her hair had crackled away behind her as she disappeared into the distance and he had always stumbled along behind her, desperately trying to catch up. Gasping for breath he'd stopped, hands on knees, to pant out his frustrations.

He had never been able to keep up, just be there when she came back; so he'd stopped trying to catch her electricity. Instead he'd sat down, grounded in the earthy here and now. He had watched the spot where the flash of her form had slipped too quickly out of sight; he'd waited. Some time later, she'd always returned; all quirky smiles and silly innuendos.

Despite their differences, their hands had fumbled together, sliding against one another in a long echo of a promised future. She'd laughed; the touch a fleeting flash of light as she'd dashed away again. He had laughed too; his chuckle more solid and grounded – attracting her lightning but unable to contain it.

She had always flitted off again; a vivid enigma in his life. He had followed because he'd had to; because he was drawn to her; because when she brushed his hand with her own the energy she'd generated kept him alive.

She'd never told him she loved him, but he'd felt it in the air that he breathed, in the vibrations of his body, in the affection of her insults. He had smiled and accepted her offering of lightning love; barely brushing past him but lighting him up with its power.

Present: Hand Holding Hand

Tension crackles through her body; her heart is splitting somehow, releasing a blinding energy as it bends towards his. The power of it frightens her. She needs him to be just as frightened in return, because his heart has already wrapped itself around hers and it hasn't split or broken or cracked – it has grown stronger, more solid. Hers is baby-fresh and new; the way it has started interlocking with his, white hot bolts of lightning mingling with the solid eternity of earth, is terrifying in its permanence.

She knows he will always follow, but she has to test it anyway. She eggs the Doctor on to visit ever more frightening planets and situations because she needs it proven, over and over again, that the one she's chosen will risk his comfort for her.

He thinks about running; she can see it in his eyes. There's a momentary panic every time; a brief longing for peace and tranquillity, comfort and stability. He will never run, though; she knows he doesn't trust her to follow. She doesn't even know if she trusts herself to do it.

Her energy crackles and burns, flying off in so many directions without purpose. She has been searching for something to steer her course, to channel all her boundless energy but she hasn't found an anchor; there is nothing to give weight to her electrifying dreams and make them possible.

He takes her hand, fingers sliding between hers, and suddenly everything comes into focus. All her energy spears down to the point where their fingers cross; coming back to her through the linked fingers is a warmth, strong and steady. Her heart beats – which have been flitting here and there with the impulses of her energy – swarm together and reach out to him, trying to break the bounds of her chest to twist themselves around his.

She doesn't tell him that she loves him; she lets him know through the twitch of her fingers closing around his, through the blazing kiss she presses to his lips, through the way her body vibrates with energy as she leans into him.

Future: Hand Clasping Hand

They will stand, side by side, looking out over the completion of eternity. They will have a future, and that means so much when they remember how their pasts had been erased. The universe will blaze with the promise of their possibilities; the time machine at their disposal will guarantee they will always have time and opportunity to test them out.

She will look down at their hands, clasped tightly together; it will be impossible to know which fingers are hers and which are his. One of his fingers will rub across her knuckle and the jolt of electricity that will crackle between them won't be formless and random anymore. No longer flighty and skidding from one thing to another; this time the energy will be focused, deep. Intense.

He will feel her sigh in his chest as she leans her head against his. His heart will clasp itself more tightly around hers, and hers will beat more strongly as it wraps itself around his in return. He will draw energy from her lightning vividness; she will draw strength from his solid warmth.

Together, they will be unstoppable. Where one runs, the other will follow. There will be no more running away; no more testing, no more waiting. There will be only promise and adventure and togetherness.

They will do all this – and more – tomorrow and all the tomorrows after; today they are newly married and finally whole. Hands and hearts twined together, following each other.

'I love you.' It is a whisper, a breath on the breeze that stirs through their reception. The words vibrate with their combined energy in a feedback loop to each other. They hold the promise of the future shimmering in front of them.

Lightning will be centred by earth; earth will be galvanised by lightning. There will be no more running away; only running. Together.