Inadvertent St Mungo's Setup

Percy's sick with a bad case of the Wizard flu, to where he needs hospitalization. Next to him, is another young boy his age...except he's there for a different reason entirely. They meet and become friends, in which Percy learns Graham is no ordinary boy. When Percy leaves, Graham is unusually sad to see him go. The reason why? Read to see! Implied pre-slash! Percy/Graham!