On the way out of the passage, Black tells Harry that he's his godfather and invites Harry to live with him once his name gets cleared.
Harry is thrilled and accepts immediately.
Black smiles and Harry is struck by how much younger he looks.
As they emerge outside, a cloud moves and reveals a full moon shining brightly.
Hermione realizes that Lupin didn't take his potion tonight and Lupin starts to transform.
Black transforms into a dog again and jumps at werewolf Lupin to keep him away from Harry and Hermione.
Meanwhile, Peter grabs Lupin's wand, knocks out Ron, and turns back into a rat and runs away.
Black runs after rat-Peter and Harry and Hermione follow him.
But then a group of Dementors surround the group.
Hermione tries to help Harry cast a Patronus charm at his prompting but the Dementors overwhelm her and she passes out (finally, not just Harry!).
Sirius is out as well and Harry is the last one standing.
The Dementor near him lowers his hood.
"Where there should have been eyes, there was only thin, gray, scabbed skin, stretched blankly over empty sockets. But there was a mouth [...] a gaping , shapeless hole, sucking the air with the sound of a death rattle" (20.67).
Pardon us while we run away screaming.
The Dementor leans down to suck out Harry's soul.
But then a bright while light appears and drives the Dementors back.
As Harry passes out, he sees a familiar looking figure reaching out to pat a silvery animal.