the_debt_of_time

Once Hermione was safely inside the tent on a bed that Sirius enlarged, he pulled
open a small black mediwitch kit and began pouring Pain Relief Potion and Blood
Replenishing Potion down her throat.
By the time Harry and Ron dared to enter the tent, Sirius was already in his
Animagus form at the foot of Hermione's bed, standing guard over her sleeping form.
And there he remained.
Quietly, the two boys discussed the Horcrux while they waited for Hermione to
wake or for Sirius to change back. When it became obvious that they should each take a
turn wearing the locket, Sirius stepped off the bed and inclined his head toward Harry,
silently requesting the locket be placed on him.
And so the days went on.
Sirius kept vigil over Hermione's recovery, shifting into human form only when
changing her bandages, feeding her potions, or waking her enough to give her the
opportunity to eat—though they had little food available. On those occasions, he said as
little as possible, refusing to meet her eyes though she pleaded with him to look at her.
Unable to let her see him break, Sirius retreated into his Animagus form knowing that it
was near impossible for her to read the expression on his face that way.
The locket, unfortunately, made everything worse.
Sirius wore it at night and would dream of Azkaban and dementors. He saw visions
of James and Lily dying, of Peter's ugly, twisted sneer, and of a girl he loved vanishing into
nothingness, leaving him alone in the world. He was grateful to be rid of the bloody thing
each morning, but he observed with frustrated intensity as the Horcrux infected the other
two wizards.
Harry withdrew into himself, and Sirius kept a watchful eye, often removing the
locket early if he noticed Harry being weighed down by it too quickly. Ron complained
constantly, though a warning growl from Padfoot shut him up instantly.
Despite her attempts, Sirius insisted that the piece of Voldemort's soul not touch
any part of Hermione at any time.