Cass was amazed - and extremely impressed. Where he didn't know what to do or say, Percy didn't even seem to hesitate. Correcting him, talking of crayons and explaining things in ways that Aiden seemed to understand immediately.
Watching the two, he realised just how lost he'd be without Percy. It was also the first time he started to actually believe that they might be all right, that this could, somehow, work itself out for the best for all of them.