Sirius Black: Enough talk,Remus! C'mon, let's kill him!
Professor Lupin: Wait!
Sirius Black: I did my waiting! Twelve years of it! In Azkaban!
Professor Lupin: Very well, kill him. But wait one more minute. Harry has the right to know why.
Harry: I know why! You betrayed my parents! You're the reason they're dead!
Professor Lupin: No, Harry, it wasn't him! Somebody did betray your parents, but it was somebody who, until quite recently, I believed to be dead.
Harry: Who was it then?
Sirius Black: Peter Pettigrew! And he's in this room, right now! Come out, come out, Peter! Come out and play!