The last person Zac expects in the room next door is a girl like Mia, angry and feisty with questionable taste in music. In the real world, he wouldn't-couldn't-be friends with her.

In hospital different rules apply, and what begins as a knock on the wall leads to a note-then a friendship neither of them sees coming. You need courage to be in hospital; different courage to be back in the real world. In one of these worlds Zac needs Mia. And in the other Mia needs Zac. Or maybe they both need each other, always.