If asked, Maz Carter would tell you that the single best day of her Hogwarts years was when she graduated, leaving Sirius Black behind. Sirius Black would (dramatically) tell you that the worst day of his life was when he learned Maz Carter was a member of the Order of the Phoenix. When Maz and Sirius are reunited under dark circumstances, something had to change. It was bound to happen. But how much change is really possible? Fate has opinions.