Secret Keeper

A Secret Keeper is a person designated to keep the location of a place a secret by means of the Fidelius Charm: the secret is kept in their very soul. The Secret Keeper is the only person who is capable of revealing the protected information to others, either by informing them orally or by writing it down. This individual will become bound by the Fidelius Charm as well. If a Secret Keeper dies, all the people already aware of the secret information become Secret Keepers; this would unfortunately dilute the effect greatly; should all the people who knew of the secret die, then the secret would die with them.

Known Secret Keepers

 * Sirius Black was originally meant to be the secret keeper for James and Lily Potter, but Sirius thought Voldemort was on to him (he thought that Remus Lupin was a spy), therefore passing on the Secret Keeper to Peter Pettigrew. Albus Dumbledore originally offered to be the Potters' secret keeper, but the couple refused on trust of their friends. Pettigrew was then the new Secret Keeper for James and Lily Potter after they went into hiding during the First Wizarding War with their infant son Harry, keeping their whereabouts in Godric's Hollow a secret. However, Pettigrew was secretly a traitor to the Order of the Phoenix. He informed Lord Voldemort of the Potters' location, resulting in the murders of James and Lily and Voldemort's first defeat when the Killing Curse rebounded from Harry. Sirius Black was later believed to have murdered 12 muggles and a wizard in front of more than 50 eyewitnesses, when really Peter Pettigrew had killed them himself and went into his animagus form (Scabbers) and fled the scene with a missing finger. Sirius Black, however, caught at the scene of the crime, was blamed for the betrayal of Lily and James Potter (not knowing that Peter Pettigrew had really been the betrayer) and imprisoned in Azkaban for it without a trial.
 * Albus Dumbledore was the Secret Keeper for 12 Grimmauld Place, the Headquarters of the Order of the Phoenix, until he died in 1997, thus making all the members of the Order, along with Harry Potter, Ronald Weasley and Hermione Granger the succeeding Secret Keepers. This forced the Order to abandon it, as they erroneously believed Severus Snape to be a traitor and he knew the location.
 * In 1997, after Harry Potter, Ron Weasley, and Hermione Granger infiltrated the Ministry of Magic, they escaped to 12 Grimmauld Place, but Yaxley grabbed Hermione as the trio Apparated to the house, thus revealing it to him.
 * In 1997 and 1998, the Order of the Phoenix used many safe houses, including the Burrow, Shell Cottage, and the Tonks house, all of which were under the Fidelius Charm and maintained by various Secret Keepers.

Behind the scenes

 * Severus Snape once said that when a Secret Keeper tells someone the secret, this person is bound by the Fidelius Charm and cannot tell anyone else. However, Ron Weasley was able to tell Dobby where Shell Cottage was, despite the fact that it was under the Fidelius Charm, with Bill Weasley as the Secret Keeper . Possible explanations for the discrepancy are that Ron himself was also a Secret Keeper, that house-elves such as Dobby have ways around magic protection and concealment, or that the Fidelius Charm was not yet in effect at that time. It is also possible that since an elf's highest law is its master's bidding, Dobby was not bound by the charm.
 * It is unknown if coercion such as Veritaserum or the Imperius Curse would reveal the location that the Secret Keeper is holding, or if the Keeper has to reveal it willingly.
 * It is unknown how Harry Potter and Hermione Granger found the Potters' Cottage, as Pettigrew was still the Secret Keeper, and he did not tell either of them the house's whereabouts. However, as it was uninhabited and became a memorial, it is likely that Dumbledore lifted the Fidelius Charm after the deaths of the Potters. It could also be assumed that even though he was too young to remember it he may have still become a Secret Keeper because he lived there as a child.

Appearances

 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Deathly Hallows