(It has been established fairly well by now on here that the Fidelius charm is not the most consistent and well-explained elements in the Potterverse. But we can still try to make sense of the madness…)
When reading the books, I had always rather taken it for granted that what Peter Pettigrew, as Secret Keeper to the Potters, kept concealed was the location of the Potter house in Godric’s Hollow.
However, as pointed out by various answers and comments to this old question by Slytherincess –
- the house was clearly visible to Hagrid when he came to collect Harry, as well as to the Muggle police/firefighters/paramedics that showed up soon after, to the wizards that later turned the Potter house into a memorial, and to Hermione when she and Harry turned up
- Dumbledore must have known where the house was (and we must assume Peter wouldn’t be too eager to tell him of all people), since he was apparently able to set up various alarm spells to alert him if anything happened
In addition to this, merely concealing the location of the house itself would leave the people you’re trying to protect quite unprotected as soon as they leave to pick up groceries—as we see in Deathly Hallows when the Death Eaters outside Grimmauld Place catch glimpses of Harry, Ron, and Hermione if they Apparate a bit too far from the doorstep.
The alternative, which I am perhaps late in even thinking of, is that the secret was the Potters themselves, or at least their current location. There is some support for this:
- In Prisoner of Azkaban, chapter 10, “The Marauder’s Map”, Flitwick describes the Potters’ Fidelius charm thus:
As long as the Secret-Keeper refused to speak, You-Know-Who could search the village where Lily and James were staying for years and never find them, not even if he had his nose pressed against their sitting-room window!
- On J.K. Rowling’s old website, the answer to the question “What happens to a secret when the Secret-Keeper dies?” states:
In other words, a secret (eg, the location of a family in hiding, like the Potters) is enchanted so that it is protected by a single Keeper (in our example, Peter Pettigrew, a.k.a. Wormtail). Thenceforth nobody else – not even the subjects of the secret themselves – can divulge the secret. Even if one of the Potters had been captured, force fed Veritaserum or placed under the Imperius Curse, they would not have been able to give away the whereabouts of the other two. The only people who ever knew their precise location were those whom Wormtail had told directly, but none of them would have been able to pass on the information.
Flitwick’s wording suggests (though perhaps not peremptorily so) that it would be possible for Voldemort to have his face pressed against the Potters’ sitting-room window at all, which would of course mean that at least the house itself was not concealed.
Rowling’s answer specifically talks about location and is more unequivocal, but that interpretation also brings up a whole slew of unanswered questions and logistical difficulties (or impossibilities).
For example, if the Potters went to the shops to buy groceries, would nobody be able to see them? And if Peter revealed the secret of their location to someone, would they become invisible and unplottable again as soon as they went somewhere else? And how could Peter even possibly reveal their location unless he was standing right next to them? If they went somewhere else, he would no longer know their location himself. And, as DVK points out in this answer, if this kind of Fideliusing were possible, why did Dumbledore not do the same with Harry later on when he knew that Voldemort was after him again?1
I cannot think of any other way the Potter Fidelius could have worked. Keeping the house concealed would be the logi(sti)cally sounder and less problematic option, but there’s quite a bit of circumstantial evidence in canon that indicates that this was not it. Keeping the Potters themselves hidden seems to have more canon support, but is a logi(sti)cal nightmare that engenders far too many impossibilities and unanswered questions.
So was Peter concealing the location of the Potter house, or the location of the Potters themselves… or something entirely different?
Is there any canon evidence or Rowling interviews that we have missed in the previous Fidelius-related questions that might answer this?
1 Or perhaps rather: if Peter simply revealed the secret to Voldemort, why was Hagrid and everybody else able to see Harry subsequently? He should still be Fideliused and thus invisible and unplottable, if that is indeed how Fideliusing a person works. If that were so, of course, there would have been no books—nobody would have been able to see or hear Harry, and he would have died from starvation among the rubble within a day or two.