The reason for Dumbledore's drastic character change can be attributed to him being damaged by a ring [[Muggles' Guide to Harry Potter/Magic/Horcrux|Horcrux]], an object containing a deadly curse that should have killed him. He was able to get help from [[Muggles' Guide to Harry Potter/Characters/Severus Snape|Severus Snape]], who has kept him alive by extraordinary magical means, although only temporarily. This minute-to-minute awareness that he will soon die, and the resulting sense of urgency, is likely the cause for his changed character.
Dumbledore, speaking directly to Petunia, saysmentions that they have corresponded before. There were,in fact,actually at least four letters that we will learn of, though at this point in our reading there isn'tis anythingnothing that we can thinkbe ofattrbuted as being "correspondence". Dumbledore had writtenwrote a letter, which had beenhe left, along with Harry, on the Dursleys' doorstep [[Muggles' Guide to Harry Potter/Books/Philosopher's Stone|at the series' beginning of the series]], and the [[Muggles' Guide to Harry Potter/Magic/Howler|Howler]] which had been addressed to Petunia in [[Muggles' Guide to Harry Potter/Books/Order of the Phoenix/Chapter 2|''Harry Potter and the Order of the Phoenix'']] hasis also been revealed to have been sent by Dumbledore. There is no indication that eitherPetunia ofresponded themto had been answered by Petuniaeither, and correspondence does rather imply anthat exchangemessages ofare messagesbeing exchanged; despite this, many readers will assume that it is either one or the other of these letters to which Dumbledore is referring. However, we will learn, in [[Muggles' Guide to Harry Potter/Books/Deathly Hallows/Chapter 33|''Harry Potter and the Deathly Hallows'']], that Petunia had earlier written to Hogwarts pleading for admission, and that it was Dumbledore who had responded, todeclining her plea, refusing her on the grounds that she was unable to doperform magic. If we assume that Dumbledore had implied exchangean ofinformational informationexchange, then he can only have been referring to this first set of letters.
