We are ghosts amongst these hills
From the trees of velvet green
To the ground beneath our feet
We are ghosts
We are ghosts amongst these hills
Pressing out along the shore - James Vincent McMorrow

River:

She watches him carefully, as one would keep an eye on a predator.

She speaks quiet words into the girl's ear, half-truths and misdirection with a silver tongue he would be proud of.

She follows them along the labyrinthine hallways, higher and higher, towards his grave.

She listens as they talk, him never saying what she wants to hear, and her refusing to listen to the words he offers.

She is a ghost, travelling wherever the impossible girl goes. She's inside her head, like a tumour. (Or a god, she thinks cheekily.)

But she's not there - not really - and no one can see her, except for the one who she travels in. She doesn't like it, but those are the rules and she has to follow them, no matter how much it kills her.

Except he was never one for rules, was he?

He always knows, and he always hurts. Goodbyes are the thing that neither of them has ever mastered, for all their practice. Hello's come easily, hers always dramatic entrances, his ungraceful stumbles (on a good day). Those they can do. Those they are good at. Conversations they can manage, because it is always held under the cloud of 'spoilers!' and secrets the other cannot know. They will continue (have continued, are continuing) copingwith their diaries and the endless 'have we done?'

Their lives are two different roads – his and hers, travelling in opposite directions, only intersecting at crucial moments for but a fleeting second, before they diverge and travel alone once more.

Or maybe they are more like separate universes, living side by side and sometimes occupying the same space, but never quite meeting. Like two pieces of time not meant to touch. Their encounters are nothing but echoes of a sound, or ripples on the surface of calm water, or a desert mirage that you can never run towards fast enough.

Time is always running out for them, and she will not let him rewrite the fabric of the universe, even though she knows he would for her. Just for one more fleeting, impossible moment of joy.

So she knows she must remain mysterious and unreachable, even as he unpicks her most knotted secrets. She must find another mystery to keep him in suspense until the next time. But she knows she can never say the obvious words she wants to and so those words echo in between her heartbeats, staying silent and unspoken.

But he hears them anyway. She should have known, because he always does, after all.

She lingers after the impossible girl steps bravely to her death.

She watches as those that comforted him when she could not return from their non-existence.

She sees his devastation at the sight of the girl who saved him so many times choosing to do so again and again, because no one else – not even her - can.

(She knows he thinks it is a failure on his part. (He always does, after all.) He tries so hard to protect everyone, even those who can protect themselves. He always forgets that it begins with a choice. Because each and every person – all those bright and shining companions – that step onto his TARDIS are there because they choose to be. Because they want to be.

Free will, the one thing he can never protect humans from.)

She speaks to him. And when he hears her and speaks back, she is surprised, even though she shouldn't be. Surprises are, after all, half the reason she loves him.

She is unravelling at the edges, but she clings on frantically, effortlessly, and gives him the one thing he can never find himself.

The instant before she vanishes, she speaks another secret to the air for him to chase. She watches as he catches her words, and immediately begins to puzzle over them and figure her out once more. Really, she thinks, he must find out soon, there is no more mystery. There is no secret she could ever hide from him no matter how hard she tries.

But mostly, she gives hope. For her madman, for his impossible girl, for herself – if only she believes enough.

And for a time, it will be Theirs.