harry is 14. the Dark Lord has returned 2 months ago. hes broken his followers out of azkaban. which means harry is staying at grimmauld with his godfather, sirius. one day he gets a bit curious and goes through sirius' old things and he finds old photos of sirius with the marauders, with lily, and with a strange woman he doesnt recognise that looks oddly familiar. like he SHOULD know her. she has long straight brown, almost black, hair and looks like just as much as a rebel as sirius is. he goes to sirius and asks, who is she?

Harry: "...hey, sirius? who is she?"