During another summer with his Aunt Petunia and Uncle Vernon, Harry Potter is attacked by dementors with his cousin Dudley. After using magic to save Dudley and himself, Harry is expelled from Hogwarts but the decision is later rescinded. Harry is whisked off by a group of wizards to Number 12, Grimmauld Place, the home of his godfather, Sirius Black. The house also serves as the headquarters of the Order of the Phoenix. Harry's best friends, Ron Weasley and Hermione Granger explain that the Order of the Phoenix is a secret organization led by Hogwarts headmaster Albus Dumbledore, dedicated to fighting the evil Lord Voldemort and his followers, the Death Eaters.