Nick's smile made Martha smile back, because there was nothing like a real smile, in her book. It reminded her a bit of the Doctor's, though without quite the overwhelming history behind it.

Martha licked her lips, reading his response, then laughed, gently, because the joke was at his expense even if he'd made it. She was overwhelmed with a curiosity about his story, wondering how he'd made it so far and kept a sense of humour, but figured that could wait; besides, the process was the actual fun.

"Thank you, but everything's okay," she said, "though we...we have a lot of past, him and me, so things could maybe end up being weird. Not unsafe, but weird. Stuff changes quickly, in his world."