The infamous prisoner of Azkaban, Sirius Black, has escaped. As long as
he is free, Harry is not safe. Sirius Black was imprisoned for killing
13 people, using one of the darkest magical curses. He is accused of being
responsible for the death of Harry's parents. The only clue they have to
go on is the guard's remark about overhearing Sirius Black talking in his
sleep saying, "He's at Hogwart's... he's at Hogwart's." Even behind Hogwarts
magical walls Harry is not safe.