The frame of this story occurs in the years immediately following Voldemort's downfall, when Harry would be approximately 19 years old. I have made every effort to be accurate with the canon of the text as well as real Muggle history. It should be noted, however, that I will assume that statements made by characters in the books reflect that character's perception of events at the time the statement was made – that perception may have been faulty or the world may have changed. I have made one change, which pertains to the nature of Pensives. I always thought it was ridiculous that they provided a purely 3rd-person view of one's memories and I have adjusted their function to be a bit more sensible.
In their years of battling Voldemort and his forces, Harry had shown a tenacity, a tendency toward obsessiveness that, while annoying, had often steered them well. Hermione had assumed that Harry's driven behavior had been motivated by his cause, and thus, with the war over, it would fade. She was disappointed.
Harry was obsessed, once more, with Severus Snape. He vacillated between suggesting that Snape was really evil throughout, that he must have been forced to obey Dumbedore by some sort of life debt or blood magic and voicing the possibility that Snape had never really been a Death Eater, perhaps had been a spy the whole time. When he did the former, Ron would shrug and mention that he'd never heard of any magic like that. When he did the latter, Hermione would remind Harry that Snape's decision to tell Voldemort the prophecy only made sense if one assumed that he really was loyal to the Death Eaters at the time.
Upon hearing either rejoinder, Harry would become either argue irritably or fall silent. Ron and Hermione quickly learned to avoid topics which would be likely to lead to Snape-related discussions, and with time, Harry seemed to move on. The problem was that the topic could never be entirely avoided. Snape's name was famous, or rather, infamous. No matter how many times Harry had tried to tell the wizarding world of Snape's heroism, he still heard mothers scolding their children, "Quit bickering or Severus Snape will get you!" and he still read Daily Prophet articles which blithely described political maneuver as a "Snape-level betrayal." Snape was a household name for everything foul.
Harry occasionally badgered his friends with questions about Snape, grasping at the slim possibility that they still held a detail or two not previously shared.
"I have no idea," said Ron, "and why does it matter anyway?"
This was the wrong thing to say.
And it explained why Ron's protests were ignored when Harry explained the plan he had arrived at: They were going to write Snape's biography.
Very short prologue, but don't worry, Chapter 1 will be out in the next 24 hours. Actually, don't worry because it's just fanfiction. If you were really worried, I would humbly suggest that you have more serious problems than simply waiting for plot developments.