Unbeknownst to Harry, Professor Lupin was coming back from the Forbidden Forest that early March morning when he ran into him in the Entrance Hall.

"Harry!" Lupin exclaimed, "What are you doing up so early? And on a weekend?"

"Draco is about to get out of quidditch practice." Harry said. Lupin nodded.

Harry knew well that Lupin was not thrilled about his friendship with Draco, but he also respected Harry enough to not dwell on it.

"That's nice," said Lupin. "What are you getting up to?"

"Probably go to the lake." Harry shrugged. "What are you up to so early on a weekend, professor?"

"Oh, me?" Harry sensed that Lupin might be hiding something, but he can't be sure. "Just taking a walk. I like the cool wind in the morning in the spring."

Suddenly, Harry had an idea. How did he not think of this in the archives room?

"Professor,"

"Yes?"

"Can I ask you a question?"

"Sure, go ahead…"

"Did you know Sirius Black?" Harry asked, "back in your Hogwarts year?"

Remus looked around, worried about the possibility of someone overhearing them.

"I did." Remus admitted.

"Were you friends?"

"Where is this coming from, Harry?"

Pause. Is Harry gonna incriminate himself by admitting breaking into the archives?

He looked around to make sure no one's overhearing them. "Hogwarts archives," he then answered.

Remus simply smirked. Breaking into the Hogwarts archives is such a James thing to do.

"How about you stop by my office today," Remus proposed, "and I can answer all your questions about…" one of the Slytherin quidditch players walked by them on her way back from practice, "… Dementors?" Lupin finished his sentence.

"Can Draco come?"

"He absolutely cannot."

And so, Harry made his way to Lupin's office later that day. Lupin made tea.

"Tea?" Remus offer, and Harry politely declined.

"You had questions about Sirius Black." Lupin said, getting straight to the point.

"Yes," said Harry. "Black had lots of detentions with Peter Pettigrew, my father, and occasionally you."

"Yes," Lupin confirmed. "I managed to stay out of trouble for most of my time here."

"Were the four of you friends?"

"Yes," said Lupin, "we were."

"What happened?"

"I suppose," said Lupin, somewhat dramatically, "the war happened."

Harry seemed puzzled.

"My father was friends with a Death Eater and a mass murderer?"

Lupin seemed uneasy.

"You're holding back on me." Harry said.

"I am."

"What are you hiding?"

Lupin sighed.

"I am afraid I cannot implicate you in this," said Lupin, "that would be very irresponsible of me."

Harry frowned. "Are you connected to Black?" Harry jerked out of his chair.

"No, Harry. I only have your best interest at heart."

"Then you'd tell me everything you know about Black, or I would take this to Dumbledore." Harry threatened.

"There's no need to involve Dumbledore."

"Then tell me what you know."

"Sirius Black is innocent!"

Harry looked at Remus, not knowing if this a joke or if he had lost his mind.

"He was responsible for the death of my parents," Harry said, gradually getting louder. "People witnessed him kill thirteen innocent people including his former best friend: Peter Pettigrew."

"That's what I thought too, Harry!" Remus jumped to deescalate and appease, "that's what I thought, but I've come across new evidence that suggests otherwise."

"What is that evidence?"

"I'll show you." Lupin said, and turned around, looking for something. He pulled out an old parchment and a cropped article from the Daily Prophet. After a closer look, Harry recognized it as the Ginny Weasley funeral article.

"What is this?"

"For this to make sense," Lupin began, "you should know that…" he stopped.

"What?" Harry urged a hesitant Lupin.

"What I tell you here stays between us, alright?"

Harry considered, and then, hesitantly, nodded.

"I'm a werewolf."

"Say what?"

Lupin folded up his sleeves to reveal his scars.

"Does Dumbledore know that?"

"Yes." Lupin said, before continuing, "when James, Sirius, and Peter found out, instead of abandoning me, they decided to be there for me."

Lupin told Harry about how his three friends became Animagi to keep him company during the full-moon.

"Wait," Harry stopped him, "the huge black dog that's been following me since summer is Sirius Black?"

"He's been following you since summer?"

"So," Harry ignored Lupin's question "if he wanted to kill me, he could've done it then."

"But he didn't," said Lupin. This is also news to him. Sirius did not mention visiting Harry.

"And you said my father was also an Animagus?"

"Yes, a deer."

"And what was Pettigrew?"

"A rat." Lupin said, as he pushed forward the article from the Daily Prophet.

Harry looked at the article. Lupin watched as his confused expressions turned into realization. His eyes widened, and his finger jumped to the article, pointing at the rat on Ron's shoulder.

"You're telling me this is Peter Pettigrew?" Harry said in disbelief. "I don't believe you."

"I know." Lupin said, "I did not believe it either."

"A street full of people witnessed him getting murdered by Sirius Black."

"Leaving only a…" Lupin said, letting Harry finish.

"A finger?" Harry said, not really knowing how that's relevant.

"Look at the rat's feet in the picture."

Harry tried, but his sight was not extremely good.

"Here, I'll help you out." Lupin cast an enhancement spell on the picture, making it much clearer.

"He's missing a finger!" Harry pointed at the rat's picture again.

"That's not all!" Lupin said, and directed Harry's attention to the old parchment. He touched with his wand, and ink appeared on it.

"This is a map of Hogwarts," Lupin introduced it. "What's special about this map is: you can see everyone in the castle at all time." He said, and showed Harry a map of his own office. In there, there were two black dots with the name "Harry Potter" and "Remus Lupin" next to them.

"Woah!" Harry said, amazed by the map, before looking up, and asking the key question. "Does this map recognize Animagi as well?"

Lupin simply smiled, and flipped the pages in the map. He reached the Gryffindor common room, and showed Harry. There were four dots on it: Ron Weasley, Dean Thomas, Seamus Finnegan, and…

"Peter Pettigrew," Harry was astonished by this. "How do we know this map works?"

"It does."

"You sound certain."

"I am."

"What does this mean?"

"What do you think it means?"

Harry stopped to think. A street full of people still saw Sirius Black attack Pettigrew. It makes sense that Pettigrew would run away and hide. But, why stay hidden after Black was sent to Azkaban? Unless…

"It doesn't make sense…"

"What is Pettigrew hiding from?" Lupin asked the question that Harry's been thinking.