"You can't see it." Dad cleared his throat. He was standing in front of Ali's class, about to give a talk. "It isn't like measles or mumps. It's not like when you break your leg. And it's definitely not catching, like when you get a cold."

Ali listened, her fingers crossed. If her father couldn't make them understand, nobody could.

And then nobody would know what it felt like to have a brother like Max, who is always dancing out of Ali's reach.