It's unlocked. He can't believe his luck.
The interior of the TARDIS — his TARDIS, he's already calling it in his mind, and the gentle hum of this gorgeous machine, the most beautiful thing he's ever seen, seems to agree with him — is white and metal and spartan. Factory settings, and old factory settings at that. There's nothing fashionable or flashy or even really functional about any of it, this dusty museum piece of a ship.
He loves it.
Then he looks a little closer at the central console and mulls over the fact that, genius or no, this particular bit of larceny is going to be a bit difficult — given that not only is he quite a few pilots short, but TARDIS piloting was one of the classes he'd failed legitimately, rather than intentionally, at the Academy.
The sound of Susan’s voice startles him, even though he knows she’s there, idling quietly somewhere behind him. "This is a beautiful TARDIS," she says softly, coming up next to him where he’s standing near the console. Her eyes roam over the central apparatus, up and down the Time Rotor, and there's something glittering in them that he recognizes, that he feels too.
"Yes, my dear. It certainly is." He runs a hand over the dials and knobs, starts familiarizing himself with the layout. "However, I'm afraid that it requires more than one to fly."
Susan smiles, and she puts her hand over his where it's resting on the console.
Everything he’s far too proper to express out loud bubbles merrily in her voice, all youthful enthusiasm and genuine excitement. She squeezes his hand and says, "I'll help you, Grandfather."
They see the stars; every planet and system and galaxy he's ever read about or caught secondhand glimpses of but never seen with his own eyes. His granddaughter discards her name the same way he'd discarded his. And because she is his granddaughter, she disregards convention and picks a name from another planet entirely.
"It's from Earth, Grandfather. Susan. That's a lovely name, isn't it?"
It's from a book, she had said. He never can figure out which, because at the time he hadn’t asked. It hadn't seemed important.
(Many, many years later, he will pore over the library’s collection of Earth literature with something resembling obsession, trying to decide which of the hundreds of thousands of books she could’ve pulled the name from).
Susan doesn't really help fly the TARDIS, but that's all right with him, because really, the TARDIS is his, and he's hers.
That might sound daft and sentimental, but that's why he'll never say it out loud.
He tries not to go back to the places he took Susan.
He thinks about doing it, sometimes, when his travels bring him close to the edges of times and places they'd once been to together. After all, it's not as though he avoids whole cities or planets or time periods — not on purpose, anyways. He takes Rose to Hadrian's Rome, brings Martha to ancient Jerusalem, shows Donna 22nd-century Paris. He takes Amy and Rory to dozens upon dozens of planets and systems and galaxies that he'd once seen through his granddaughter's eyes, all those centuries ago.
But there are little places, specific places, that he won't go back to.
Cafés in Paris, where Susan had eaten éclairs for the first time; sun-browned fields outside the walls of Rome, where she'd run through the grass towards the TARDIS and yelled keep up, Grandfather, you're so terribly slow; markets in Jerusalem where he'd bought her scarves and cast-bronze trinkets and she'd declared them far more beautiful than anything they had left behind on Gallifrey.
But Susan’s gone now, slipped through his fingers and lost to time. He’s a bit scared that going back will mean he’ll only be able to see the empty spaces, the voids where Susan ought to be.
It’s not a sure thing, of course, and he’s equally afraid that if he doesn’t go back, one of these days, that the memories he’s trying so hard to preserve will fade away. The sound of Susan’s laughter in that market, high and chiming and gleeful. The sparkle in her eyes, the one reflected in those of so many companions after her, when they’d had to run for their lives in Rome. The musical sound of her voice speaking their native tongue, describing the taste of French pastry in a language with no less than forty-two different words for sweet.
After he loses Rose, the same worry begins to seize him again — but where Susan is a healing scar, albeit one he’s afraid will reopen if prodded too hard, Rose is a bleeding gash that he can’t seem to staunch. The need to know what to do with those memories, those places, is urgent in a way it never was with Susan, edged with a desperate need to have something that calls to mind Rose as she was. He feels caught between two impossible pains, paralyzed with indecision about which to choose, about which would be worse.
He tests the whole idea, briefly, when he takes Martha to New Earth. It’s a Rose place, not a Susan place, and the associated hurt is more fresh, the wound more raw. The part of him that’s always been a masochist takes some savage joy in grinding the salt in, wanting to see what will happen if he puts someone else in the empty space where Rose should be.
It all ends terribly, as he should’ve known it would.
He composes a new list of places. The cliffs outside of New New York. The chip shop at the Grand Bazaar on Publius. The breeding grounds of the flying Oora rays, on Metraxis VI. The Powell Estate.
They’re infinitesimal omissions, in the grand scheme of things. The chance he’ll ever visit any of them again is minimal, with the universe being as massive as it is.
He makes the list anyways.
No one will ever call him Grandfather again.
He hopes that a different him might hear it again, someday — that some small human voice will say it to a man with gray-streaked brown hair and a single heart, under a sky full of zeppelins.
But not this him. He’ll never hear that again.
The knowledge gnaws at him more and more the older he gets, the longer he sits alone in the TARDIS between trips to see Amy and Rory, between the mad jaunts with River that grow further and further apart as the years drag on.
The TARDIS is melancholy, unhappy without the pitter-patter of companions’ feet in her corridors, without someone other than a lonely old man to mother and take care of. She’s happy, for a time, when the Ponds come back to stay, and for a bit it’s like old times.
Then Amy and Rory are gone, suddenly, snatched up and out of his reach by the touch of an angel. He tries to tell himself it’s not the worst goodbye he’s ever had. He knows that they were happy, in the end, like Susan was happy, like he has to believe Rose was — is, with Rose it is always is — happy.
He can’t decide what to do with their places, or River’s, whose time has not come quite yet but will, someday soon.
He doesn’t want to remember. He doesn’t want to forget.
He parks the TARDIS on a cloud and leans towards forget, for a while.
He doesn’t mean to take Clara to Akhaten.
It’s one of those places that he’d put a lot of effort into avoiding, once upon a time — a Susan place, a before-the-War place, a destination crossed out and navigated around on the map of the universe in his brain.
He could say that it’s the TARDIS’ fault, that it’s that faulty navigational system taking him somewhere he doesn’t want to go yet again. But it’d only be partly true.
The truth, the whole truth, is that he’d just forgotten. He’d looked at the readouts on the monitor and briefly checked the name of the planet, grabbed his jacket and straightened his bowtie and whisked Clara out the TARDIS doors — and then he’d seen the whirl of sounds and sights and colors in the bazaar and realized oh, Akhaten.
He knows that Clara’s speaking to him, asking questions about the planet and the market and what exactly they’re here for, and dimly he registers that he’s responding to her, in an absent-minded sort of way.
The larger part of his brain, though, is paralyzed with the knowledge that somehow he’s forgotten this — not permanently, of course, but long enough that he’s broken his own rule completely by accident.
What’s supposed to be a simple sightseeing trip goes absolutely mad, of course. Things spiral out of control until he’s staring into the heart of a great burning god, yelling at it and standing his ground, because that's what he does. He doesn't walk away.
He shouts take it all, not knowing exactly what that’ll mean — not knowing, at this point, if he wants to know.
The next day, he takes Clara for éclairs in Paris.