[ At first, Serenity looks unsettled that her hunch was right and that the Doctor had no idea what had happened to Earth while he was having his adventures and battles across the galaxy...

.. but it's that one bit about being a child that has her very curious. Explaining about the Dark Moon Family would have to wait for now. ]

One can't take a real break and act like a child when they're in a place of work and serious business, Doctor. So, unless you have any suggestions...