They'd landed upon this rock - meteor, the Doctor had corrected her - too long ago for her wandering feet. He was occupied with some tinkering with the TARDIS. That was a task she'd learned long ago not to help with. That was his private time with the TARDIS, and she happily gave it to him. After all, the TARDIS was with him long before she arrived, and would be with him long after. She could accept that, at least. So she'd gone out for a walk.
"Just be careful out there. The scanners aren't picking up any life forms, but you never really know what could happen." She'd shrugged it off as a typical warning, tested the temperature and left her jacket on the railing before starting out. Now, just out of sight of the TARDIS from where she stood behind a rock outcropping, she was stopped in her tracks.
She blinked, trying to clear her eyes of dust and debris so she could be sure of what she was seeing. Because she needed to be sure. There was a low buzzing in the back of her head - their TARDIS - but in front of her was the spastic static of a television channel that just couldn't tune in. It wasn't just the sound in her head though: the actual thing in front of her was flickering. One moment a rock, then a tree, then a metal spike, then a small car, then a merchant's tent from the perpetual market on Kava, then the familiar shape of a blue phone box. As the buzzing in her head got louder, it seemed that the thing in front of her picked up on it, too, and the blue box appeared more and more often in the rotation of random shapes that paraded in front of her.
"Malfunctioning chameleon circuit," she heard herself mutter. Not a jammed or broken one, like the one on their TARDIS, which was jammed on that shape mostly because the Doctor liked it, but a chameleon circuit that was in its last gasping breaths. It was locking onto the signal most native to it and trying to adapt. It seemed to be stabilizing on the blue police box. And for a long moment, both ships looked exactly the same.
She knew the Doctor would tell her not to go in, to stay out of such an unstable ship, especially a TARDIS. If she went in, it could materialize somewhere he couldn't go to get her. And she knew that.
But she also knew that the Doctor would go in, no, he would rush in. He would tell her to stay there - a much safer proposition now that she knew how to fly the TARDIS - and sonic his way into the control room of another Time Lord's ship, exploring the mysteries of it. If he had found it first, he would have done just that.
But she had found it. And he was still in their TARDIS, tinkering with something. He was always tinkering with something. It calmed him down. And after the nightmares of the previous evening, he needed some calm.
So she didn't call for him to join her in her tentative exploration. She told herself that he needed time to himself. But she knew, from that faint buzz of their TARDIS in the back of her mind, that there would be too many unanswered questions if they went in together. She might know things she shouldn't. Worse, she might say them out loud.
The door to this duplicate blue box creaked as it opened, but the interior of the ship was terrifyingly quiet. The desktop theme was not the same as their TARDIS, but she recognized the control room all the same. Not many TARDISes were set up with entry directly into the control room. It was part of the ships dying attempt to mimic a living ship. This one wasn't even a Type 40, she realized, examining the console. It was newer, but harder used. Someone didn't care for their ship the same way the Doctor did.
Which brought her to the more immediate question: how had this TARDIS gotten here, and where was its pilot? There was a layer of dust on the console, and the buzz of this TARDIS was growing louder and more frantic in her head. It was competing with the familiar low buzz of their TARDIS in her mind, and the result was almost deafening. She looked around for any sort of clue - anything that might tip her off as to the identity of the Time Lord that had left this behind. Why here, on this rock with only ruins and no surviving civilizations? Why had it been left behind? What sort of Time Lord would leave their TARDIS? Or what sort of fate had befallen him so he couldn't leave this place?
She began to get a queasy feeling in her stomach, doubting her decision to come in here on her own. Her hand reached out, seemingly of its own accord, and touched the helmic regulator. It settled comfortably in her palm at first, feeling just like the one she was so familiar with. She wondered if she could fix this one up, perhaps to have as a spare car of sorts - keep it in their TARDIS's garage to pull out when things needed fixed.
The feel of metal and glass cracking under her touch registered a moment too slowly. What she felt instead was fire and knives - the console was exploding as the TARDIS died. She fell to the floor, a metal grate that bit into her skin with the force of impact, and looked back at where she had just been.
And there, looking back into her, was the Heart of the TARDIS.
It swirled in her head like a million trillion galaxies all coming together in a strange sort of entropic dance. It was golden, and streaks of blue and silver and every color she could name and so many more that she couldn't. It was overwhelming - she was going to drown in this space, even if a small part of her argued that it was only in her head. She was going to drown in her own mind. She was giddy at the thought of dying, as though it made sense and was amusing that she had never seen it this way before. Of course she died here - and the Doctor mourned her along with all the others he had lost, but carried on. Picked up new companions. Saved worlds she hadn't yet heard of. Had unnameable adventures.
No, she would live through this, but the scars would make her too slow for him, too hard to handle. He would leave her somewhere safe, somewhere that she could spend her too-long convalescence looking out at the stars and cursing the burns on her body and the brokenness of her mind for having to let him go.
Still wrong. The TARDIS - her TARDIS, would come to her aid, help heal her from this mess. It would purge the problem - the Time Vortex itself? - from her body, and the ship would integrate the extra power, and life would continue on as normal with Miranda Larsen and the Doctor in the TARDIS.
She locked onto the Doctor, the only constant in all of this swirling madness. She could feel the deluge encroaching on her soul, or what she imagined to be her soul - that part of her mind that was so distinctly her that any change to it would fundamentally alter things.
She thought of him in their TARDIS, busy fixing something with his sonic screwdriver, and noted each nanosecond that passed between the time he dropped to the moment it hit the grate below. He knew something was wrong, she mused. He knew, and was coming for her. She focused on him, and as she did a line seemed to extend from him - one backwards, and a million different ones forward. She traced a few of them in her mind. In one, the Doctor was dying, alone, on a planet filled with rolling pepper pots - Daleks, she thought. She retreated from that one hastily. In another, she and he were marooned on a beautiful planet, with all the amenities she could want. A home, the Doctor by her side, and she seemed happy. She lingered there, on that time line, the one where the TARDIS had been stolen from them by angels in the cemetery but it was alright, because they were together. But he was sad and burdened by something she didn't understand, but she could feel his hurt even in this hypothetical future.
She considered for a moment, but left that one behind, too. She hopped from thread to thread like an exploring spider, envisioning every future for him. Some included her - those were the ones she liked. Others did not. She did not linger on those.
Finally she came upon one, and she was there. She survived this barrage of time and space and became more like him. She bore the pain, both physical and emotional, daily, but she returned to their TARDIS where they took to the stars. Pleased, she jumped forward further in time. Here though, there was a young blonde girl. Rose, her now-infinite mind named her. Strange, since the Doctor's first companion was named Rose in Gallifreyan. Susan in English. Rose. And Rose made the Doctor smile, and Miranda thanked her for that. Rose saw this thing, this deluge, too. She was a goddess for a moment. She hopped forward again. Still Rose, though the Doctor had a new face. Regenerated, she supplied to herself. Bad wolf. The Doctor loved Rose. Miranda's heart clenched, and she hopped forward again. The Doctor with a young human doctor, desperately in love with him. The Doctor not remembering anyone before Rose... not remembering her. Donna Noble. Adam. Jack Harkness. Amelia Pond. Rory Williams. Clara Oswin, or Oswald? Stone angels, rolling pepper pots, evil tin men, lizard people, and creatures in suits that she only remembered with the part of her mind that flowed over the entirety of the universe. And then, at the end, at the very end, she reappeared.
She understood then. She could choose how hard to fight, and it would change everything. She could succumb to the burning pain that was beginning to pulse through her with each wave of color. All of time and space was screaming in her head. She could hear a child giggling on the swing, a soldier dying in battle, a father reading a bedtime story, a scientist burning his skin with a drop of spilled acid, a temp deciding to turn left instead of listening to her mother, a concerned woman making tea - and that was just the Earth timeline. They were all there - world's she'd never seen, and never would see in person, timelines that existed and could exist. All that ever was, all that is, and all that could be. She was spiraling through it all, and it was consuming her.
"Miranda!" She heard the Doctor's voice and opened her eyes. She could see herself reflected in his blue orbs - her eyes were a roiling, molten gold. She opened her mouth to speak, and traces of the same gold spilled out with her breath. "You're gonna burn! You've got to let it go!"
And in that moment, she made her choice. She let go. It rushed out of her in streaks of blue and gold and silver, brushing affectionately against the Doctor as it streamed out the door of this broken TARDIS and toward their own, which she could hear in the back of her mind calling it to her, as though welcoming a lost sister. And then it was gone. The space in her mind that had been filled with the Time Vortex was suddenly glaringly empty. Her sense were too small - too big? - for her mind now. There was so much space inside her. So much bigger on the inside.
She felt the Doctor's arms underneath her as he lifted her gently. There were cuts and burns across her face and arms, she knew. Blood smeared lazily across his jacket where she wrapped her arm around him. Her throat was parched and she could find no voice with which to speak. She rested her head against him, feeling so small and so big, this paradox of knowing everything and nothing. It was exhausting.
In the medical bay, she retained enough sense of her surroundings to know, somehow, that she had chosen. She was still too disjointed to know quite what she had chosen, but so far it included her being alive and the Doctor being near her and that he would be ok. She knew that. She forgot the rest for now, but knew he was ok. That was the most important thing. Her dry lips may have been repeating that, but there was no way for her to know. The nanogenes were doing their work on her, more work than they'd ever been asked to do. She found herself vaguely disappointed that after all that she wouldn't even get to have a scar to mark the occasion. She didn't the Doctor would mind scars. She knew he had a few from battle. She'd traced them with her fingertips. She liked that feeling, and the way it made him take in a startled little breath.
She understood that her thoughts were small, but they seemed appropriately sized for now. The nanogenes were working, and the Doctor was saying something to her. She couldn't understand him. She blinked. She could see the worry lines etched on his face now, the same ones that deepened during nightmares. It occurred to her that this was the stuff his nightmares were made of, and it made her sad to know she had caused it. She tried to focus on what he was saying. It must be important. What do you say to someone you fear might die? She wasn't going to die of course. She had seen when she was going to die, and this wasn't it. She had so much of her life left to carry on with. But he didn't know that.
She tried to focus on him again. Watched his lips as they mumbled something incoherent. Gallifreyan? As soon as she thought it, it began to piece itself together in her head. Gallifreyan. Don't leave me. Don't leave me. I need you to come back to me. You promised you'd always come back.
They were the ramblings of a desperate boy, a lost boy. And she knew what she had promised him. It had been a big promise even then. Now, having seen everything, she understood its scope for the first time, the way he must have understood it when she first uttered the words. She blinked again.
"I'm not going anywhere, Doctor." Her voice sounded raspy and thick even to her, a sound creaked out from the back of a cave, rather than her own small throat. His eyes met hers, looking at her hands where the cuts had been and sighing with relief. The nanogenes were working. They weren't dead and used up on little things, as he'd feared. They would mend her and bring her back to rights.
"Except to sleep." His voice was calmer now, and as his rough fingers brushed over the back of her hand, examining her new skin, he tried to send some of that through to her. Her mind, still gaping at the loss of the Time Vortex, was open to receive him. Calm flooded through her, and something else she couldn't quite find a name for in English. Parts of her mind that had previously been unused sparked to life, trying to provide other words in other languages that might help her. She brushed them aside, choosing instead to call it the feeling the Doctor gave her. It was true and uncomplicated. And she slept.