Author's Note: So, this break hasn't been as restful as I thought it would be, but I did not mean to let this go as long as I did. I am very sorry, and thank you so much for all of your kind words in the reviews and your patience. We are winding this one down, ladies and gentlemen, with one or two chapters remaining!
It was always going to happen.
The Doctor knew that. Martha was not his first Companion, and he knew she wouldn't be his last. For one reason or another, they all left, and it was for the best. He'd lose them eventually regardless...to old age, to accident, to violence, despite how he tried to prevent it. It was better for them to make the choice to leave. Better to go on their own terms.
And at least this time, he could see it coming.
He could see it n the way that Martha asked more and more frequently to stay longer and longer with the Winchesters, and came back to the TARDIS full of stories about her adventures with the boys. She'd talk about it while they walked on planets galaxies away from her home, while they visited times farther from her own than she could imagine.
Unfathomable places and eras, and she said, "Dean showed me how to change the oil on the Impala."
The Doctor treated a hairline fracture on her shin after a run-in with a nasty, hostile reptilian species on a planet that was slowly being drained of water until they got there and saved it, and Martha said, "Bobby's gonna make us repaint the devil's traps and sigils around the house when we get back to Sioux Falls. I think I've finally got the hang of the designs. Want me to show you?"
He took her to see the moment that the Earth coalesced into roughly its current form, and (after an appropriate moment of awe) she said, "Castiel's probably here. Oh, did I tell you what happened when we took him to the carnival when we were investigating the boys' last case?"
He sat next to her in the library, each holding a book in his native tongue—the language of a race that never existed within the time line she inhabited, and yet one of its sons sat with her—and she said, "Doctor, I think I'm in love with Dean."
And the Doctor could hardly find it in himself to be unhappy about it.
Yes, this meant that he'd lose her. But he would have lost her anyway. And this way, he was losing her to someone who needed her more than he did. He was losing her to someone that he cared about, someone whose happiness meant a great deal to him, but more importantly he was losing her to someone who loved her even more than he did. He'd lose her to a life he didn't want for her, a life of fear and violence and uncertainty, but, as she reminded him frequently, he was not her father. She was an adult, and she'd made her decision.
And perhaps this would mean that he'd get to keep her in his life more than he would otherwise. It wasn't like the Winchesters weren't constantly on his radar.
So the Doctor stood next to Castiel in front of Singer Salvage and gazed out bemusedly as the Impala roared to life. He watched Martha swing herself into the passenger's seat at the last moment before Dean (had to be Dean) gunned it and took off down the dusty lane as though they were pursued by...the sorts of things they were normally pursued by.
He turned to Castiel, who was likewise staring after them, and said, "Seems your wild boys have absconded with my Companion."
Castiel turned to him, eyes narrowed as usual. "They are hardly my boys," he intoned.
The Doctor scoffed, waving a hand to emphasize his dismissal of the statement. "Please," he said. "You might not want to claim them, but they've latched on to you, and it's too late now, my friend. Humans are hard to extract, once they've attached."
"I did not say I wanted them gone," Castiel said, as though concerned that the Doctor had truly mistaken him.
"No," the Doctor replied, "of course not. But it is rather like having two hyperactive toddlers as your responsibility."
"With a vehicle," Castiel added, morose.
The car left their field of vision (well, the Doctor's field of vision, at least; he still hadn't figured out what Castiel's enhanced senses could detect), and the Doctor smiled softly. "They make each other happy," he said quietly.
"They do," Castiel agreed. "Dean is rarely as at peace as he is when Martha is near. It is...a relief to feel that in his soul."
"She wants to stay," the Doctor continued, and Castiel stilled, knowing what that meant to the Time Lord. "For good. She hasn't said she wants to leave, yet, but I know that she will, and soon."
He ran a hand through his hair and tried to avoid Castiel's keen gaze, but found himself unable to keep from meeting it. The angel's expression was far more understanding than the Doctor had expected, and he said, "I will protect her, Doctor. As though she were my charge."
The Doctor nodded, smiling sadly. "Thank you, Castiel," he said. "That comforts me."
And it did.
Because this was always going to happen. Martha was always going to leave the Doctor, one way or another, and to have Castiel look out for her was the next best thing to looking out for her himself.
But there was one other thing that was always going to happen, and the Doctor dreaded it.
Because eventually, and by now sooner rather than later, Martha was going to find the Gospels.
And it would change everything.