Muggles' Guide to Harry Potter/Places/Riddle Manor

General Overview
Riddle Manor is the ancestral home of Tom Marvolo Riddle's Muggle father, Tom Riddle. For much of this story, it stands empty.

Extended Description
In Harry Potter and the Goblet of Fire we read the story of how Tom Riddle Sr. and his parents were found dead one morning fifty years ago, and how the gardener, Frank Bryce, was suspected of their murders until it was found that they apparently had not been murdered by anything, but had simply died... possibly of fright. We also see how Lord Voldemort has moved into that house, and we see him killing Frank. Other clues through the course of the book lead us to believe that Voldemort is using the house as his base of operations; in fact, according to what we are later told by Barty Crouch, he has moved his base of operations to Bartemius Crouch's house, where he and Wormtail take up residence after Mr. Crouch is placed under the Imperius curse. After Crouch's escape, Voldemort and Wormtail do return to Riddle Manor, and remain there until the end of the book.

While no direct mention of the Manor is made in other books, we do see some of its environs in Professor Dumbledore's Pensieve in Harry Potter and the Half-Blood Prince.

Analysis
Riddle Manor is not, strictly speaking, necessary. It is true that a shut-in, poverty-stricken girl like Merope Gaunt is most likely to become infatuated with the local lord of the Manor, as he will have all the appropriate accouterments – attendants, property, jewelery – and financial means to lift our poor peasant out of her downtrodden existence and into the lap of luxury. Though likely any reasonably well-off Muggle would have served the purpose, it is much more romantic if the lord of the manor falls for the peasant girl; and Merope seems to have been preconditioned to be romantic. One must assume that Riddle Manor is created purely to highlight the romance that Merope can force with her phial of love potion.

After the death of the Riddle family, the house, we are told, reverted to some mysterious people in London who tried, unsuccessfully, to rent it out. While we are never told who the people in London are, it is possible that they are, knowingly or otherwise, agents of Tom Marvolo Riddle, who could have assumed that he was the heir, being the late Tom Riddle's son. One wonders, though, whether he would not try to dispose of anything that reminded him of his Muggle father. As the house certainly must remind him of the late Tom Riddle, one must wonder why Tom Marvolo Riddle would choose to live in it.

While evidence in the text does indicate that Tom Riddle and Merope Gaunt did get married (Dumbledore uses the terms "husband" and "wife" to refer to them, and refers to Merope as "Merope Riddle" at least once), one wonders exactly how title to Riddle Manor got transferred. As the manor and lands were purely Muggle property, Tom Marvolo Riddle would have necessarily had to deal with the Muggles he hated, in order to secure his claim to the property and arrange agents to take care of it. One has a rather ludicrous image of Tom Marvolo Riddle, wand concealed up his sleeve, dealing with an army of faceless bureaucrats.

In fact, except for the one night when Frank Bryce was killed, we do not know where Voldemort was living. He could well have chosen to leave Riddle Manor that night for some place with less associations for him. Or he could have chosen to stay there, as a way of spiting his deceased father and grandparents. We do know that he was in the environs of Little Hangleton in June, when the Triwizard Tournament ended.

Greater Picture
It is tempting to believe that Voldemort created a Horcrux, the one embedded in the ring of the Peverells that Voldemort had stolen from his uncle Morfin Gaunt, via the murder of Tom Riddle Sr. Evidence in Harry Potter and the Half-Blood Prince is inconclusive: Riddle's conversation with Professor Slughorn, that we see in the Pensieve, suggests that Riddle did not yet know how to create a Horcrux. During that conversation, Tom asks about Horcruxes, and we see that Tom is wearing the Gaunt ring. It is possible that Tom had already created a Horcrux, in the ring, and his question is designed to put Slughorn more at ease about his abilities and ideas; we can see that the main thrust of his questions is more to do with the possibility of creating multiple Horcruxes. Dumbledore does state that Tom had no longer wanted to wear the ring once it was a Horcrux, and while this must be supposition on Dumbledore's part, he was usually accurate in his guesses. Additionally, we have Tom's look of triumph when he has received the information about Horcruxes from Slughorn; given the author's usual efficiency, we have to think that he has done more here than just hoodwink Slughorn. Tom must have gotten some real information from Slughorn to merit that amount of joy.

The author has stated that it was the death of Tom's father that allowed him to create his first Horcrux; presumably he only chose to hide the Horcrux away, rather than keeping it close to himself, when he had created a second one. This would imply that Dumbledore had made a trivial error; as mentioned, Dumbledore believed at that time that Tom knew how to make a Horcrux, but not that he had done so. Dumbledore likely believed that the ring had only been made into a Horcrux via the death of Moaning Myrtle; at that point, likely, Tom stopped wearing the ring, hiding it in the Gaunt shack, because he now had the Diary as a backup. In this case, Tom's look of triumph at the conclusion of his talk with Slughorn probably relates to his having learned that making multiple Horcruxes was possible.

It is possible that Frank Bryce's murder was used to create the final Horcrux of the set that Voldemort was planning; bringing the circle to closure, by generating the last piece of his "immortality" in the abandoned home of his hated father, would likely have appealed to Voldemort's sense of humour. It is also possible that Bertha Jorkins' death was used to create a Horcrux; at that point, he would have been keen to finish the full set, and would have had no way to know that Frank would so conveniently present himself. The author has stated in an interview that the sixth and final Horcrux was created by means of the death of Bertha Jorkins, which does make it more of a matter of expedience than a plan. This is borne out by the non-snake-like behaviour of Nagini when passing by Frank Bryce in the hallway; Nagini likely would have behaved quite differently if she had not already been carrying a fragment of Voldemort's soul.