Tracking down the Doctor is easy, if you know what to look for. Finding the same one you’ve lost is the tricky part.
This time, Missy is carrying precious cargo. The brain, original and intact, is the important part, and she’d been very careful with that - that was the part the Doctor would care about, and there wasn’t much else left to salvage anyway. The body that houses it is a replica. She'd had to make personal sacrifices she didn't even want to think about, and the whole project had taken days. The parts were the highest quality, chosen with precision from the exact year that saw the peak of android customisation. Expensive. Probably. She hadn't paid for them, of course. What will the Doctor think, when she returns his pet to him as good as new? What better selfless act is there than preserving the creature that means nothing to her and everything to him?
Her creature often forgets to be grateful. It curls up and falls silent. It presses its fingers into the flesh of its arms and imagines that it can tell the difference between real skin and artificial. It stares at its reflection again and again. And then, even later, when it seems to have accepted its form, it malfunctions. Parts of the body, rejected by their owner, stop moving for no mechanical reason. This is the most inconvenient part. The body may be more sturdy than the original, but the mind is fragile. Basic maintenance brings back indistinct memories of the scent of blood and disinfectant and the sound of metal on metal. Missy has learned not to let her watch. If the Doctor had wanted to teach her how to treat a human gently, he should have broken Bill sooner.
She’s much improved now. She stands at the console under the pretense of watching the screen, examining her reflection in the purple light. Missy watches her from her seat under no pretense at all. Today’s little trip taught them nothing, another day wasted. Alone, she might have found the Doctor weeks ago, but she’s learned the hard way that humans need rest. It's a terrible waste of time and slows their progress to a crawl. When they do go out, she sees the Doctor's mark on his pet. The girl is almost quick enough to keep up with her and though they always return empty-handed, her spirits improve with each stop. And though still cautious, the human has warmed to her. It seems ten years and a wide open universe will make a short-lived lifeform less picky in its choice of friends.
‘If things continue like this,’ Missy says, ‘we’re going to have to start outsourcing.’
‘Outsourcing?’ Bill frowns, set on guard by the sudden comment.
‘Asking his little friends.’ She waves a hand vaguely. ‘Not that I expect them to know anything I don’t, but I might get something out of them. His last human is still flying around somewhere out there.’
‘Last human?’
‘That’s right.’ Missy smiles. ‘Did you think you were special?’
‘No,’ she says, frowning, not looking at her. ‘Of course not. I mean, he's, like, a hundred times my age. I wouldn't be the first.’
It's not a lie. How boring. But the humility is charming, too. The girl has a good sense of her place in the world, unlike his other pets, so desperate to prove themselves his soulmate. She finds herself still watching her, seeing the cogs turn in her mind.
‘Maybe…’ Bill says slowly, still frowning. ‘Is it even worth finding him? What if he doesn't… remember me.’ She touches her cheek absently. ‘Recognise me.’
The likeness is good. Missy can't tell the difference, but Bill looks in the mirror and sees a stranger. It's awfully human of her. No time lord would make a fuss over such minor differences - the placement of marks and freckles, the precise growth pattern of hair. In lives past, Missy has made do with less. But perhaps there is something different in Bill, some natural improvement created accidentally by her skilled hand, because in these past few weeks the girl has begun to draw her eye more.
‘You know what I mean,’ Bill insists. ‘He's… 2000, whatever, years old. I only knew him for a few months, really. That's nothing. I mean, you - You would forget about me as soon as you had the chance, right? Even if he cares so much about Earth, one human life is so… small, to him.’
Missy doesn't allow herself the opportunity to ask herself how long she'll remember Bill, once she's gone.
‘What do you want, then?’ she says. ‘And after all this work to track him down! You can't expect me to keep you.’
‘Oh. Right, sorry.’
Missy watches her. She can almost see them - human thoughts in a human brain in a mechanical body. She doesn't like to see such a troubled expression marring the face of her creation. Missy has never wanted to understand a human before. But sometimes Bill sees something which inspires in her such visible wonder that she can't help but follow her gaze. She never sees what Bill sees. Any natural beauty the universe may hold is not hers to behold. But sometimes, in the reflection in Bill’s bright eyes, she catches a glimpse.
‘Well…’ she murmurs. ‘I suppose I could find a use for you.’
If Bill hears her, she gives no indication. Her hands grip the console. She stares blankly into the screen. Missy never knows what to say to her. But she has found, through trial and error, one quick fix for her anxieties.
‘Here, Bill,’ she calls her, as a human might call a dog. She pats the side of the chair.
It's almost a ritual now. Bill's expression softens; relief of some kind, at the summon or at not having to ask herself. She walks to her and settles to her knees on the floor beside her, head resting against the leather of the seat, just barely touching Missy's thigh. Missy's hand meets her neck and snakes slowly up to meet her temple.
She knows her creature’s mind inside and out. To soothe it is a simple task. Bill’s body soon relaxes under her touch.
What would the Doctor think, seeing his pet kneeling at her feet, mind at her fingertips? Bill doesn't want to think about that, but Missy can't help but take the boost to her ego that comes with imagining it. What would the Doctor think?
But there's nothing sinister about it, really. Free from the vault and satisfied that her human won't leave her, the impulse to dominate its mind has faded. She hasn't yet learned how to calm it with words, and this is much easier. Sometimes, when she feels generous, she allows the girl to rest her head against her chest and hopes the Doctor hasn't taught her too much about Time Lord biology.
She could be right. Perhaps the Doctor, too, will see the tiny differences in her and mistake her for a trick. Then what could she do but keep her? Without reward, it was supposed to be, but if he fails her after all her hard work… she might have earned a consolation prize.