"It's empty," I said. This unprepossessing bag was Mum's most valued possession?
"I know." Mum's smile was full of secrets. "It's the bag I was carrying when I met the Doctor."
She'd told me about the Doctor when she thought I was old enough. I was never sure I believed the story. "I don't get it."
She sat on the floor, beside me. "The bag is empty. That's the point--that's what the Doctor is. He takes away everything you have . . . and in return, he gives you everything you could be. And sometimes, if you're very lucky . . . you really fly."