Martha put her head down on Jack's shoulder, tracing slow circles on his back. It was the folly of a life longer than what was the norm. The knowledge that you were going too outlive everyone... There had been many nights that Martha had stayed awake trying to wrap her mind around the implications of what Jack's life was. Back when they'd first met, the idea of an impossible thing... Traveling with the doctor you saw eight impossible things before breakfast, but Jack was special. He was different. It was one of the things that she loved about him. But that question. The knowledge that while she could spend the rest of her life with him... It wasn't something she liked thinking about, and did her very best to ignore.
The idea of him alone, the fact that she knew what was coming... She hadn't thought about the Face of Boe for such a long time. The thoughts seemed to come at the worst of times. It was something that she was determined to change. She didn't care that it was supposed to be impossible.
Martha ran a hand through Jack's hair as he cupped her cheek, her free hand moving to cover his. The look in his eyes broke her heart. She tried to put a small smile on but couldn't bring herself to do so. If someone had told her all those years ago that she would be here, now, when she'd first met Jack - hitching a ride on the TARDIS - she might not have believed it. She hadn't known what to expect back then. She'd been much younger, but now. She couldn't picture a life that didn't include a him. A future that didn't include him. She knew that - of all the things that Jack Harkness held, this fear was one he faced every day. It cut through like a knife. She'd been seeing it in the way he held himself since Ianto's disappearance and in the way he'd looked at her. That fear - even if he hadn't realized it - was written on his face.
She squeezed his hand and wrapped her arm around him. "And you won't." She knew that the words may have sounded hollow. How did you promise something like that to a man who had seen eons? But she meant it. Every word. "I know that it's hard to accept, but there is nothing, not on earth, not in space, that can take me away from you. And if it did," she paused, tilting her head to the side, "well I'd just have to do whatever it took to get home. And I wouldn't stop until I was." This much was true. She didn't know if it helped. They had been through too much done too much to just let things happen. They'd done everything they could to keep Ianto with them, but they'd failed... and she knew that it ate at them.
"I did a lot of reading while I was with the Doctor." She couldn't count the time that she'd spent in the TARDIS library. "There's a belief, on Thetoria, a planet in a system that I can't even pronounce the name of, that every living thing has someone or some thing that they're meant for. That they are literally connected by unseen forces and will be drawn together. It doesn't matter the distance it doesn't matter how long it takes. But once it's done, there is no escaping it. You're bound." She allowed herself a small smile. "For good or ill. No matter what..." He was it or her. And she would fight tooth and nail to stay or get back to him.