It is well known among Harry Potter fans that Hagrid has the "tightest" lips in the world. Therefore, when Harry asked him how he had managed to get a dragon egg, Hagrid excitedly blurted out that he had let slip the Three-headed Dog's weakness—that it would fall asleep if it heard music.
Seeing Hagrid spill the secret without a moment's hesitation, Ye Feng couldn't help but wonder if Hagrid was playing the fool and deliberately leaking the Three-headed Dog's weakness to Harry. Of course, that secret *was* meant to be leaked to Harry in the first place, only it wasn't Hagrid who had orchestrated it, but Dumbledore.
Ye Feng found it utterly impossible to believe that Dumbledore had no idea what Hagrid was like. Dumbledore knew full well that Hagrid couldn't keep a secret and was easily tricked into giving away information, yet he still chose to have Hagrid retrieve the Sorcerer's Stone and assigned that very same Three-headed Dog to guard the door to the underground chamber. If that wasn't Dumbledore's doing on purpose, who would believe it?
Chapter 55