It was an odd feeling, having Jack back on the TARDIS. That unspeakable wrongness of his immortal existence had worn off, or at least down to a long buried niggle at the back of the Doctor's brain.

His final companion. The Doctor wasn't going through that again. Jack until the end, as it probably always should have been.

"Making yourself at home I see," the Doctor smiled, circling the console and watching Jack. "You know, for all the bravado you put on, I know something about you," he said, his voice a silky purr. "A secret."