The night of Sirius Black's infiltration was one of managed chaos. The Gryffindor students were hastily bedded down in the Great Hall, sleeping in purple sleeping bags under the watchful eyes of the prefects and Professor Dumbledore himself. The air was thick with fear and excited whispers.
Harry, lying awake, felt a strange, cold dread. The man who had betrayed his parents, the man who had led Voldemort to their door, was somewhere in the castle. He was close.
Ariana, however, lay in her own sleeping bag, her mind a silent, whirring engine of calculation. The variables were all in place. Sirius Black was in the castle. The Dementors were outside. The truth of Peter Pettigrew's betrayal was a dormant bomb waiting to be detonated. And Pettigrew himself, in his Animagus form as Ron's pet rat, Scabbers, was likely just a few feet away, sleeping in Ron's bag.
Her summer of research had not been an academic exercise. It had been preparation for this exact moment. She had the court transcripts, the timeline of events, the logical proof of Black's innocence and Pettigrew's treachery. The question was no longer if she should reveal it, but how and when. To simply announce it to the world would be chaotic and would likely result in Pettigrew escaping in the confusion. No, the unveiling had to be a controlled demolition, a sequence of events she would orchestrate to ensure the correct outcome.
And the first step in that sequence was to bring the person most affected by the truth into the fold. She could not, would not, move forward without Harry's knowledge and consent. To do so would be to treat him as a pawn, the very thing Dumbledore was so often guilty of.
Two days passed. The castle was on high alert. Security trolls patrolled the corridors, and the Fat Lady was eventually found and persuaded to return, though she would only do so if provided with extra protection. The fear of Black was a constant, oppressive presence.
It was during this time that Ariana sought out Harry. She found him in a quiet, sunlit window seat in the Gryffindor common room, staring out at the grounds, his expression troubled. She sat down opposite him, her presence calm and focused.
"Harry," she began, her voice low and serious, creating a bubble of privacy around them. "We need to talk about Sirius Black."
Harry flinched at the name, his knuckles whitening as he gripped the stone windowsill. "What about him? He's a murderer. He betrayed my parents."
"That is the official narrative," Ariana said, her gaze steady and unwavering. "It is also a lie." Harry stared at her, his green eyes wide with a mixture of shock, confusion, and a dawning, defensive anger. "What are you talking about? Everyone knows he was their Secret-Keeper!"
"Everyone is mistaken," Ariana stated simply. She did not present her findings as a theory or a possibility. She presented them as fact. "I have spent a considerable amount of time reviewing the Ministry transcripts and historical records from that period. The narrative has critical inconsistencies."
She began to lay out the evidence with the cool, dispassionate clarity of a barrister presenting her case. "The Fidelius Charm protects a secret by magically embedding it within the soul of a single living person, the Secret-Keeper. No one, not even the people the secret is about, can reveal it unless the Secret-Keeper chooses to. James and Lily Potter chose Sirius Black to be their SecretKeeper. He was their best friend, your godfather. It was the logical choice."
She paused, letting him absorb the information. "However, at the last minute, Black had an idea. He believed he was too obvious a target. He reasoned that Voldemort would come after him directly. So, he persuaded your parents to switch. To use someone Voldemort would never suspect, someone weak and unassuming, whom they all considered a friend."
Her periwinkle eyes held his, and she delivered the final, devastating blow. "They switched the Secret-Keeper to Peter Pettigrew."
The name hung in the air. Peter Pettigrew. The man Black had supposedly murdered. The man who had been posthumously awarded the Order of Merlin, Second Class.
"No," Harry whispered, shaking his head in disbelief. "That's not possible. Black killed him. They only found his finger."
"Pettigrew was an unregistered Animagus," Ariana continued, her voice relentless but not unkind. "A skill he learned here at Hogwarts, alongside your father and Sirius Black. His form is that of a rat. He cut off his own finger, created a massive magical explosion to simulate his own death, and killed twelve Muggles in the process. He framed Black for everything and then, as a rat, he vanished. He has been in hiding ever since."
Harry felt the world tilt on its axis. Everything he thought he knew about his past, about the night his parents died, was being systematically dismantled before his eyes.
"Sirius Black is innocent, Harry," Ariana said, her voice softening with a profound empathy. "He did not betray your parents. He was framed by the man who did. He has spent twelve years in Azkaban for a crime he did not commit. His escape, his infiltration of this castle… he is not here to harm you. He is here for one reason: to find and kill Peter Pettigrew. He is here for revenge. He is here for justice."
She fell silent, allowing Harry the space to process the monumental, world-altering truth she had just given him. He stared at her, his mind reeling, trying to reconcile the image of the grinning, handsome man from his photo album with the supposed mass murderer, and now, with the tortured, innocent victim of a terrible betrayal.
"Why?" Harry finally managed to ask, his voice hoarse. "Why are you telling me this now?"
"Because I have a plan," Ariana answered. "A plan to expose Pettigrew, exonerate Sirius, and rewrite the last twelve years of history. But it is a plan that directly concerns you, your godfather, and the memory of your parents. It is not a decision I would ever make without you. I will not blindside you with this, Harry. You are not a piece on a chessboard to be moved without your knowledge. You are the person who matters most in this equation."
She held his gaze, her own full of a fierce, protective loyalty. "I have located Peter Pettigrew. I know where he is. I know how to corner him. But I will not act until you have had time to process this truth. Until you tell me you are ready. The choice of when and how we proceed… is yours."
She had done it. She had armed him not with a spell or a shield, but with the truth. She had given him back his own story, placing the power of its conclusion firmly in his hands.