Settled in the story
When was Slytherin's locket first mentioned?
A heavy locket nobody could open was thrown out with the rubbish at Grimmauld Place two books before it mattered. The trail runs from that cupboard through a pawnshop, a ministry office, and a thief's stash to the sword that finally opened it.
This thread gives away a resolved story point
The clue
A heavy locket that nobody in the Black family house could open, tossed into a sack of dark clutter during a clean-out — two books before anyone on the page had heard the word Horcrux.
The trail
- Book 5 · The Noble and Most Ancient House of Black
The clean-out of 12 Grimmauld Place turns up biting silverware, a musical box that nearly puts the whole house to sleep — and a heavy locket that none of them can open. It goes into the sack with the rest of the dark clutter. The scene plays it as housekeeping.
- Book 6 · The House of Gaunt
In the first memory lesson, a girl in a ruined cottage wears the locket as her family's proof of descent from Slytherin. It is the same object, suddenly with a pedigree: the heirloom of the Gaunts, and not long after this memory, sold in desperation for a handful of gold.
- Book 6 · Lord Voldemort's Request
An elderly house-elf's memory shows the locket again, in a collector's drawing room, produced to impress a charming young Tom Riddle. Within days the collector is dead, the elf carries the blame, and the locket has vanished along with the visitor.
- Book 7 · Kreacher's Tale
The old elf of Grimmauld Place tells the missing half: his master Regulus swapped the locket in the cave and ordered this one destroyed. It survived the elf's best efforts and went back into the house's clutter — which is where a certain thief later looted it from.
- Book 7 · The Muggle-Born Registration Commission
Mundungus Fletcher sold it, and the trail resurfaces around Dolores Umbridge's neck at the Ministry, worn as a family heirloom and taken as a bribe. It leaves her office around a rescuer's neck, which is how the Horcrux finally changes hands on purpose.
- Book 7 · The Silver Doe
The payoff lands in a frozen wood. Ron Weasley, who has carried the thing's whispers around his own neck for months, opens it and destroys it with the sword of Gryffindor. The cupboard junk from book five was load-bearing all along.
The payoff
The locket is Salazar Slytherin's, made a Horcrux, hidden in the cave, swapped by Regulus Black, and destroyed by Ron Weasley in the Forest of Dean. Its first appearance — as rubbish nobody could open — is the quietest plant in the series: already sealed, already cursed, already waiting.