Jack was all but ready to argue the fact. Jack did a lot of things. He met a lot of people, and he was convinced he had met someone like him. Someone just like him, in fact.

But no. No, he supposed this man was right. He was unique, and Jack was sure of that. Sure of it but not entirely sure why he was so sure.

"Careful," Jack said, slightly warily as the Doctor stood. He looked up at him with a slight frown.

"If things are changing in the universe, that can't be good. They don't change themselves, not for any reason, so that means someone did something to change them."

He wiped a hand up over his face and shook his head. "Okay. Well. Guess I'd better find out what. You just... get back to your box."