Somewhere along the way, the Doctor had gained a third heart.
It throbbed in the center of his chest, an unexpected syncopation, a shocking addition to his age-old rhythms.
-Alive…Alive…Alive…Alive-
It was his lifeline. After all the death and destruction he had seen, he had been unable to stop, he had wrought—still, Rose Tyler was alive. She had trusted him completely, and he had not failed her.
But it was also a countdown, a wired bomb ticking down to his final destruction. For Rose Tyler would not be alive forever. There were so many dangers in her new world, and while he couldn't endanger her anymore, nor could he protect her. Even if it wasn't his fault this time….he didn't think that third heart could beat one she was—
And when he rested, cocooned by the TARDIS (for she had loved Rose too, and he did not mourn or nurse loneliness alone), with -Bad-Wolf…Bad-Wolf- thumping in his chest, he allowed himself an idle fantasy. Perhaps with this biological anomaly, this evolution, he was a new species, no longer needing to carry the burden of survival of his people. Perhaps when his third heart failed, it would drown out his other two that drummed Survive-Survive...Survive-Survive…and so perhaps he, too, could—
But "morning" always came before he finished the thought, and he shoved it away. And if his excitement was a bit more manic, his craving for danger even less tempered by caution, his time with each new companion a bit shorter than the last—well, there was no one around who knew him well enough to notice.
He made sure of that.
