The Doctor wasn't sure why he'd been summoned.
He'd visited before to cheer up the children who were stuck there, given out sweets and done magic tricks, played his guitar a few times but he doesn't think they would have called him back for that- hell- they didn't even have his number.
That's why he's running.
Or at least that's what he tells himself.
He's just really confused. No one knows his number so how did they get it? Who gave it to them?
It's a lot better of a reason than the fact he feels terrified and is almost trembling with the dread that's been going through him since picking up his phone. That would be silly- that's Nardole's job.
He doesn't even know the Doctor's here.
It's better this way- he doubts Nardole would approve of him running off for even a few minutes.
He bursts through the automatic doors, feet taking him around turns and corners easily as he gets closer and closer to this feeling of horror. It tries to swallow him, tearing at his mind like a strong wind as he pushes against it.
No, no, no.
What's happening?
He knows something is wrong- terribly, awfully wrong- but what is it?
He's running now- can't stop his feet as people pull themselves to the sides of the corridor, chastising him who doesn't wait to hear them.
No, no, no.
This isn't- this can't be- can it?
He pushes through door after door, not seeing the shining floor beneath his feet as his panic grows in the proximity to- what? What is it? Why is he feeling like this?
A door in the way is locked- he sonics it open and steps through and up to the desk.
The human there looks at him in confusion and surprise.
"How did you get in sir?" She asks, eyebrows dipping a little in confusion.
The Doctor pauses for a millisecond that feels like forever, mind thrown onto a different track as he struggles to compute against the fear and worry washing over his mind.
"Door was open." He says eventually, "I'm sorry- I've been called in and I was wondering if-" He begins, fingers resting against the polished surface of the tabletop.
"Oh- that's strange- we'll have to get that fixed." The human says, looking past him to the doors. She turns back to him.
"I'm sorry- did you say you were here for someone?" She asks.
"Yes." The Doctor says, rubbing a hand over his mouth and chin. He blinks, tries to calm himself.
"I'm- I just got a call to come here. I'm not sure who from- they didn't say but-" He cuts himself off, taking a deep breath through his nose.
The woman frowns, eyes going towards the desk.
"Ah- yes. I remember." She says quietly, "I'm not sure- What relation did they say you were?"
"I-" The Doctor stops, tries to remember, "A friend. I think- thing is I have so many friends-" He begins to babble and the woman cuts him off.
"She's just down the hall- second door on the right." The human supplies.
The Doctor thanks her, attempting a smile which doesn't want to come through on the best of days and so today is probably worse than normal.
He takes off, second door on the right, and closes it behind him.
The room is oddly silent aside from the beeps and soft whirring of machinery and the blue curtain is drawn the whole way around the bed.
Gently the Doctor turns the beeping down, the buzz of his sonic joining the soundscape for a few moments.
He waits behind the curtains.
If this person had his number they must have known he would come.
He can hear breathing on the other side. Shallow.
Gently he pushes aside the curtain, only turning to look when he's pulled it shut behind him.
On the bed lies a woman.
"No." The Doctor murmurs, stepping closer. His hand reaches for her of its own accord.
She shifts, face pale and blue eyes bright as they find him. Her lips part in an expression he somehow knows is happy.
"You came." She whispers, blinking slowly and swallowing.
Her hand, just as washed out as her face, extends towards him too. She manages the strength to raise it a little rather than just swinging it over the side of the bed.
"Doctor." She says, smile growing wide.
The Time Lord rushes forwards, wraps his hands around hers the best he can with the drip in them.
"Why here? Why now? What happened?" He asks, throat tight as he gently sits down on the edge of the bed, clenching his teeth.
She seems confused for a moment then tries to shake her head, deciding after a moment that it's too much expenditure of energy she doesn't have and giving in with a sigh.
"Can't tell you. Not happened for you yet. Just needed to see you one last time." She admits, eyes flickering down to her hand in his.
"I've confused them- they don't know what to do with me. It's quite funny." She says before he can speak, attempting to change the tone.
"Missy." The Doctor whispers, gaze on hers as she struggles to meet his.
She freezes, eyes darting to the side and staying there.
He runs his thumb over her fingers, waiting.
"I didn't- I didn't know how much it would hurt." She murmurs, eyes slipping closed, "To hear you call me that again. For the last time." She says.
"No."
"Doctor. This is the end." The Mistress admits.
"No." The Doctor says, fingers tightening around hers a little.
It's enough for her to wince and he releases them apologetically, letting her palm lay flat against his.
"I can't- I can't regenerate any more. Even a new cycle wouldn't-" She says, eyes glistening as she licks her lips and looks at him.
"You can't!" He begs her, "No- there must be a way. Some way to-" The Doctor declares.
The Mistress says nothing, staring up at him with an expression between hope and defeat, lips parted and chin tilted upwards and brow creased. Desperation.
"I wish I could- could stay." She says, soft gasp disrupting her speech. Tears finally slip free.
"I would stay for you if I could- forever, Doctor." She promises, voice growing hoarse as she struggles to breathe.
"No. Please don't do this to me. Not again Missy! Please!" He begs, taking up both her hands this time and carefully pressing them both between his.
"Please don't do this!" He pleads, voice breaking as she blurs in his vision, his tears slipping against her too-pale skin.
"Please Missy!" The Time Lord cries, bending his head down to hers and wrapping his arms around her limp body. Her head lolls a little as he holds her to him.
There's the last of her soft breaths against his ear.
The Doctor weeps, holding the body of his best friend, knowing it's the real end because of the sound of his name as it dripped from her lips.
He pulls her close, kissing her brow again and again as he lifts her into his arms, feeling her weight. Dead weight.
"I'm sorry. I'm sorry. I'm so sorry."