Speculation on Two Specula
(Sorry, couldn’t resist the pun. Not that I tried. For the Latin-illiterati, that’s “speculation on two mirrors.”)
Why did Sirius Black have both sides of the paired mirrors he and James had used during separate detentions to communicate privately?
If the two Marauders had used the set for so trivial a purpose as to talk to each other when separated for punishment, wouldn’t they have been using them to talk securely during the war? If so, how did Sirius end up with James’s half of the set after his death?
I mean, canon doesn’t show us Sirius roaring up on his flying motorbike and ransacking the wrecked house (or James’s cooling body) to find the other half of a now-useless-to-communicate-with-James mirror set before giving the bike to Hagrid and apparating off in hot pursuit of that traitor Wormtail.
(How the mirrors ended up in Grimmauld Place seems simple enough-on Sirius’s condemnation to Azkaban his personal effects were all sent to his next of kin. And Walburga may have hated her son’s choices, but she still housed the effects of her last surviving son.)
Well, maybe James did have his half, and it was James’s failure to answer his mirror as well as Peter’s inexplicable absence from his hidey-hole that made Padfoot’s hackles rise that Halloween.
Or maybe he did not.
*
We saw another paired device in canon in which each half of the set communicated (only) with the other: the Vanishing Cabinets. With which Draco managed to bypass ALL the protections on Hogwarts and introduce Death Eaters to its halls.
As the mirrors, apparently, bypassed whatever magical barriers the detention-assigning professor would surely have placed to keep those two “closer than brothers” troublemakers from gleefully high-fiving each other while scrubbing….
(I peg the mirror set as another Potter family heirloom lent by doting parents to their darling boy. Anyone who’d give their teen son [who was constantly in detention for assaulting other students] a priceless invisibility cloak “so I can sneak down to the kitchens for a snack, Mum, you know how I get puckish just before bed and they don’t LET you call an elf for cocoa and a biscuit there”….)
(Or, per Swythyv, perhaps another Potter non-heirloom….)
But anyhow, Sirius gave that mirror to Harry when he wanted Harry to have a way to reach him, fast, if he needed to be bailed out of trouble with Snape.
What if those mirrors were also a means to reach its mate’s holder? Fast?
A locater of some kind, as well as a walkie-talkie?
As in: where did Tom get the spell he adapted to make it possible for his Death Eaters to Apparate blind when summoned, and end up in his vicinity? And then know instinctively which way to go to enter Tom’s august presence? When he summoned his servants to Little Hangleton, they drifted in from all directions. Did canon suggest that Tom Senior’s gravesite was one of their usual meeting places, and when they found themselves in that neighborhood they knew where to go to meet their lord?
Moreover, we saw in DH that even a piece of the second mirror would act as the whole.
If so, that mirror set was an incredible hole in the security system set up by Fidelius. Suppose Sirius were captured, and his half of the set with him. Then his captor could use the mirror to Apparate to James’s vicinity.
Of course, he couldn’t see James, mirror or not.
But suppose Voldemort broke Sirius’s mirror into twenty pieces, and gave each to a Death Eater, and the twenty Apparated at dead at night and found themselves forming a circle… it wouldn’t matter that they couldn’t see the house, or the happy family snug therein. Cast Fiendfyre within that circle, and the Potters would be done.
(In fact, even if the mirrors couldn’t be used as an apparition guide, if there were any way to use them as a directional indicator, this would still work. Station the twenty piece-holders around Britain, and work their way in to pinpoint a blank place in the universe in Godric’s Hollow. Indeed, this could be done by one person with repeated casts; it would just take longer to pinpoint the hole in the universe where the mirror’s brother’s holder must be hiding.)
So long as someone inside the Fidelius held one mirror, and someone outside it held the other, that risk would be real. (And I bet it was the resident Muggleborn who pointed that out, some night when Sirius was reassuring her he could get to them fast to help so long as he had even a fragment of James’s brother-mirror.)
So either both mirrors should be held by James, or both by Sirius. But if James had them, he couldn’t use them at all.
Whereas if Sirius had both, he could use them to set up private communications with someone else. Say, with the Potter’s Secret Keeper.
Except Padfoot just couldn’t bear to profane the mirrors by turning Prongs’s over to that little arselicker Wormtail, so he kept delaying, day by day….
And left the pair in his flat when he set out in a righteous fury to avenge Prongs’s death.
Does that work?