"Mhm. We travelled together for a while." The Doctor wasn't sure what else to say to that, so he just tightened his hold on Jack's hand and, after a few moments, lifted it to his lips so he could kiss it, ever so similar to the gesture Jack pulled off so well. He was fairly sure that from him it was more awkward than suave, but at least it filled the silence while they thought about those left behind for whatever reason.

Those that left and those that got left and those that just didn't make it.

He sighed and closed his eyes, covering them with his arm. "I can't give him up. Not anymore than I can give myself up. I'm sorry, Jack. I'm selfish."