Dumbledore heard a crash from his office. He jumped up from his chair and walked quickly out of his office, down the steps and he stopped. Suddenly. He saw, in the distance, Lucius Malfoy, lying spread eagle on the floor while his House-elf, Dobby stood in front of Harry in a stance that made it appear, to Dumbledore that Dobby was protecting Harry. How odd, that the elf would turn on his master. And then he saw it, in Dobby's hand, a filthy, smelly black sock that he didn't doubt belonged to Harry Potter himself. It appeared, that Dobby was a Free Elf. Dumbledore stood by as he watched Lucius Malfoy storm off around the corner and out of the building. Harry also left, but not before wishing Dobby well in his new life as a Free Elf, leaving Dobby, unknowingly alone in the corridor with Albus Dumbledore. Dobby turned around and his eyes settled on Dumbledore, standing tall at the end of the corridor.
'Master Dumbledore, Sir, Dobby is sorry for having to do that to Mr Malfoy, Sir, he was very mean to Master Harry and Dobby had to help him, Sir!' Dobby rushed his apology and explanation and failed to notice that the Headmaster did not appear to be in anyway angry or upset by the Elf's behaviour.
'Dobby, I do not think you need to apologise for assisting Mr Potter in matters which I could not have helped, I do think, however, that if it is acceptable for you, that I might take that which you have in your hand?' Dumbledore gestured to the diary in Dobby's right hand, however, misunderstanding Dobby suddenly became very animated.
'No Sir, I want to keep this one forever, I will hang it on my wall, or wear it every day! For it is the sock of Master Harry Potter and it is the sock that has freed Dobby from them horrible Masters!'
'No no Dobby, I did not mean the sock, by all means you may keep that for ever, it was given to you, and it is yours, I was talking about the object in your other hand, that rather beaten up old diary you have there?' Dumbledore tried to reassure Dobby that his sock would not be taken, and as comprehension dawned on Dobby the relief was clear on his face.
'Oh yes, Master Dumbledore, Sir! You have it, you have it, Sir! But you must be careful, it was mean object at Master Malfoy's house, Sir! One of the meanest!' Dobby shuddered from the memories and handed the book back to Dumbledore.
'Of course, Dobby. Thank you.' And with that the Headmaster returned to his office, eager to finally evaluate what made this Diary act the way it did. Many ideas already formulating, though none as close as he would get once he had taken a dip into his Pensieve.
Dumbledore sat down at his desk and opened up the Diary. Nothing was written on any of the pages despite Miss Weasley and Harry Potter using this Diary. He looked on the back and discovered a date. A very important date. A date which would set him as being the Deputy Head of this very school, a Transfiguration Teacher, and Head of Gryffindor House. A date that was famous for people of a certain generation. The exact year a girl had died at the school. The same year Tom Riddle had first opened the Chamber of Secrets. And suddenly, comprehension dawning on him, Dumbledore stood up and walked to his pensieve. Over the years he had compiled quite a collection of memories attaining to a certain Mr Tom Riddle, looking for any that had occurred in this year, or those either side, Dumbledore began to re watch the old memories.
A few hours later Dumbledore returned to the present, now well in to the night, and having watched many of the memories multiple times, the old man was very tired. He sat down at his desk and rested his chin on his hands, thinking of one particular memory.
'I was in the library the other day, in the restricted section, and I came across a term I didn't quite understand. Horcruxes' Dumbledore picked up the diary, tracing the new hole with his finger. Could this have been a Horcrux? Dumbledore, being the wizened old wizard that he was, knew a great deal about a great amount of things, however, this particular form of very dark magic was so dark that in fact, Dumbledore could never bring himself to read about it. Slowly, he stood up, walked through the door on his left and arrived at the Headmaster's private library. A collection of work that had been handed down from Headmaster to Headmaster, and the entire load of books that after closer inspection, were removed from the library. Dumbledore himself had removed a large majority of the books that now sat in his library when he first became the Headmaster, including all that had directions and descriptions of Horcruxes.
Dumbledore picked up one book that he had previously glanced through, knowing that it would give him the information needed he sat down at his desk once again to begin reading about one of the darkest bits of magic recognised.
After a couple hours, with many reading breaks in between, Dumbledore's head rose from behind the book. He slammed it down on the table and once again picked up the diary.
'Well it fits the description. And Harry killed it with a Basilisk fang. And Miss Weasley was 'possessed' because she poured her soul into it' Suddenly everything became clear, Dumbledore knew that this was a Horcrux, everything made sense and yet, before he could even figure out what to do with it, it was done. Harry had destroyed it. It was done. Voldemort was mortal again. Or was he? There had been little information about the whereabouts of Voldemort since his last attempt at returning. But, was this an attempt to return? Or was this merely Lucius Malfoy clearing out all his Dark objects?
And so, it was Voldemort again. The heir of Slytherin had possessed a little girl and forced her to do his bidding, luckily this time, not resulting in any deaths, but upset and pain for families and friends of the petrified victims. But this time was the last. Dumbledore now knew of the entrance to the Chamber, and whilst he was certain he would not like to remove such a historical and secret part of the castle he would detract attention from it however he possibly could. Although he knew that while the basilisk lay dead on the Chamber floor the danger was no longer there. Should another heir appear there would be no monster to do it's bidding.
But Dumbledore was not worried, he thought to himself as he grew more tired, of if he should, or should not tell Harry about the Horcrux.
The Horcrux has been destroyed. There is no risk of him coming back, he is mortal again. Is there any need to tell Harry? No, he is twelve, twelve is not much better than eleven after all. He is far too young to be understanding the actions involved in creating a Horcrux. It would be pointless to tell him this information, information that is not going to help him in any way nor is it going to convince him of what he must do later. The information is useless. There was a Horcrux, now there is not. But what if he asks the dreaded question again? 'Why me?' Should I then tell him of the prophecy? He is still a child, much too young. Since this Horcrux has been destroyed, it might be years until Voldemort's return. I can tell Harry all about it then. No I will not tell him now.