Rose watches the Doctor softly; Mickey finally figures it out, and tugs on Rose's sleeve: "Come on, Rose. It's time you showed me around the rest of this place." Thank God for Mickey Smith. And though she's timid and though she's hesitant, this is the kind of thing Mickey understands, and Rose knows that -- she's walked his simple halls sufficiently -- and so she goes with him, and shows him the TARDIS: her halls and her mirrors and gates and wardrobes. She glances back, only once -- that's her sin, always; watch -- and the Doctor plays for her benefit, tapping the screen and pulling switches, before they're well and truly gone. He takes out the letter, and begins to read.
My Dear Doctor.
The path has never seemed more slow, and yet I fear I am nearing its end. Reason tells me that you and I are unlikely to meet again. But I think I shall not listen to reason. I have seen the world inside your head, and know that all things are possible. Hurry though, my love. My days grow shorter now, and I am so very weak.
God speed, my Lonely Angel.
I almost didn't transcribe it, because I think it's private. I mean I literally -- how gay is that? -- wanted to deny you that letter, so you could find it elsewhere, and preserve some sound of echoes in the halls, some kind of darkness in the secret. Some dancing you can't imagine. Which is (only 1% admittedly) twee-er than I'm willing to go, so I'll distract you with this: "And was the day of my delight As pure and perfect as I say? ...I hold it true, whate'er befall; I feel it, when I sorrow most; 'Tis better to have loved and lost Than never to have loved at all."
Too easy? Or too hard? The Doctor doesn't know. He tucks the letter away again, and looks at the fireplace on his monitor, dancing in cheery flames. He presses a key or two, leaving the fireplace in darkness. There's no girl in the fireplace now; no need to have a fireplace at all. What good's a fireplace, with no girl inside? He watches this physical space for a spiritual object that is gone with the sound of wings, and then looks up. Up, as the engines begin to run. Up, up, up.
Outside the TARDIS, the vacuum wind of a big blue steel angel picks up, and takes the Lonely God, and the only woman he knows, his only friend, and hers in turn, to their next destination. She disappears, this blue angel beast, and behind her is parked a portrait of Reinette, labeled thus: "Madame de Pompadour, 1721 - 1764."