Harry has not been having a good summer.  Voldemort's back, but nobody is telling Harry anything.  Then a dementor attacks him, and before Harry has a moment to think, he's required to go to a Ministry hearing to see if he's expelled from Hogwarts and whisked away to Sirius' house, and introduced to Dumbledore's Order of the Phoenix.  But even then he's being kept away from meetings and feeling alienated, even when Ron and Hermione are there.  Throw in a ministry-appointed Defense Against the Dark Arts teacher who seems bent ruling Hogwarts with an iron fist, and this is shaping up to be Harry's worst year at Hogwarts yet.

Harry Potter and the Order of the Phoenix