Harry Potter and Severus Snape are both framed for the deaths of some high ranked ministry workers and Death Eaters. With both sides after them, Dumbledore forces them into hiding until they can clear their names.

"Apparently the students thought that he would Avada Kedavra them on the spot if they accidentally met his eyes. Dunderheads." Snape's time as Headmaster, from his point of view. [complete, prequel posted]