One plot point left hanging at the end of ''[[Muggles' Guide to Harry Potter/Books/Half-Blood Prince|Harry Potter and the Half-Blood Prince]]'' is a '''missing''' Horcrux. Dumbledore and Harry have clearly discovered where the Horcrux is hidden, but the Horcrux itself is gone, replaced with a substitute locket by one "R.A.B." Both the substitute locket, and the unknown "R. A. B." (presumed to be [[Muggles' Guide to Harry Potter/Characters/Regulus Black|Regulus Black]]), are keys to the "real" locket's whereabouts. In ''[[Muggles' Guide to Harry Potter/Books/Order of the Phoenix|Harry Potter and the Order of the Phoenix]]'', the [[Muggles' Guide to Harry Potter/Characters/Black Family|Black family]] house is being used surreptitiously as a headquarters for the [[Muggles' Guide to Harry Potter/Characters#Order of the Phoenix|Order of the Phoenix]]. When [[Muggles' Guide to Harry Potter/Characters/Sirius Black|Sirius]] and [[Muggles' Guide to Harry Potter/Characters/Molly Weasley|Molly]] undertake to clean the house, [[Muggles' Guide to Harry Potter/Characters/Kreacher|Kreacher]] undermines this effort –, along with [[Muggles' Guide to Harry Potter/Characters/Walburga Black|Mrs. Black's]] mad screaming portrait, undermines this effort. Listed among the objects being discarded is, "a heavy locket that none of them could open." Harry, having retreated to Grimmauld Place after the the [[Muggles' Guide to Harry Potter/Magic/Ministry of Magic|Ministry]] has fallen in [[Muggles' Guide to Harry Potter/Books/Deathly Hallows|''Harry Potter and the Deathly Hallows'']], sees Regulus' name on a bedroom door, and deduces that this must be the "R.A.B." connected to the substitute locket. After fruitlessly searching Regulus' room, Hermione recalls the locket that they had earlier tried to discard. The locket had been hidden by Kreacher, then stolen by [[Muggles' Guide to Harry Potter/Characters/Mundungus Fletcher|Mundungus Fletcher]], who was busily looting 12 Grimmauld Place during the early parts of ''Harry Potter and the Half-Blood Prince''. Mundungus willhas, in turn, have had it extorted away from him by [[Muggles' Guide to Harry Potter/Characters/Dolores Umbridge|Dolores Umbridge]], resulting in Harry making an expedition into the [[Muggles' Guide to Harry Potter/Places/Ministry of Magic|Ministry]] to retrieve it.
AlsoAs ofnoted noteabove, Voldemort split his soul into seven parts. In many cultures and religions, seven is a significant number, possibly because it is the "most magical number", as Riddle says; hints of this magical power likely strayed into our Muggle world.
