Awakening in the hospital wing, Harry and Hermione are told that Black has been sentenced to have his soul sucked out by Dementors. Professor Dumbledore tells Harry and Hermione to use Hermione's time-turner, a device she has been using to attend simultaneous classes, to go back in time and save Buckbeak and Sirius. They rescue Buckbeak and watch themselves attacked by Dementors. Harry then casts the Patronus that drives away the Dementors. Harry and Hermione ride Buckbeak to the tower where Black is held and break him out. Black escapes on Buckbeak.