The year is 2003. Harry, Ron, and Hermione are 22 years old. All three are actively working in the Ministry of Magic. A new fad has hit the wizarding world by storm -- linked journals. You write in your own journal, and your message appears to anyone else who owns one. They write in theirs, it appears immediately on your own pages.
Harry, for all he has accomplished, is still something of a broken young man. His parents and Godfather are still dead, and now all the people who could have accurately told him about them are dead as well. All that remain are people from his own generation, and those who didn't know his parents well enough to satisfy him. But he remembers that night in the Ministry of Magic, in the Department of Mysteries.
He remembers the Veil that took Sirius from him, so soon after they met.
And he has an idea.
What would happen, he wonders, if he threw one of the linked journals through the veil? Where would it land? On the other side, in the world of the dead? The world he only momentarily touched when he died himself, at Voldemort's hand?