Ophelia Jackson was a fan of the Harry Potter universe, and when she died at the age of 37, she was reborn as Sirius Orion Black.
Becoming the hope of the house of Black.
Changing things for the better or worse.
Takes place shortly after book 5: Sirius Black is dead, but a memory of him still remains. Rummaging through Padfoot's old possessions, Remus discovers a bit of the past in a diary. Similar to Tom Riddle's diary expreience, with a 6th year (16yr old) Sirius Black.