(Note: Resisted the urge to rename the original title for this chapter to Sherlock Holmes.)
After listening to his account, Sherlock couldn't help but shake his head.
"What a shameful betrayal."
At the same time, he frowned, recalling what Lupin had said earlier.
"You said that after they discovered you were a Werewolf, they specifically learned a high-level Transfiguration spell to keep you company?"
Lupin did not answer Sherlock's question immediately.
He silently looked up at the full moon hanging high in the night sky outside the shack, remaining silent for a long while.
After a while, he spoke slowly.
"I have always felt guilty about this, and I have even hesitated about whether or not to tell Dumbledore. Now that I have already told you, even if Dumbledore is disappointed in me, after tonight, I will tell him the whole story."
Sherlock did not speak; he assumed the posture of a listener, wanting to hear Lupin finish the story.
"James, Sirius, and Pettigrew, in order to come and keep me company when I transformed into a Werewolf, specifically learned the highly advanced Animagus Transfiguration spell. This magic allows a Wizard to transform into an animal, and Werewolves are only interested in attacking humans; they have no intention of attacking animals."
"James and Sirius had great talent in magic; they both learned this spell on their own, while Pettigrew, with their combined help, also mastered the Animagus transformation. After learning it, they never reported it to the Ministry of Magic and would take me, transformed into a Werewolf, to wander around Hogsmeade."
"I was very young at the time and didn't consider how dangerous it was. It wasn't just that one incident with Snape; there were many other times I almost hurt others, but fortunately, I still managed to graduate from Hogwarts safely."
"Sirius knows the Animagus spell, and it is very likely he used it to sneak into Hogwarts. But I have never dared to tell Dumbledore about this; to say it would be equivalent to telling him about the things I did as a student. I am afraid he will be disappointed in me!"
Lupin held his wolf head in his hands. He looked deeply pained, but his tone carried a sense of relief after finally saying everything.
"The students in the Castle all like me and think I am a good teacher, but I have been cowardly and kept hesitating to tell the truth."
Sherlock ignored Lupin's current emotions because Lupin's words reminded him of something. He stared intently at the Werewolf opposite him, who was blaming himself incessantly, and asked quickly,
"Do you still remember what animal Black's Animagus form transformed into?"
"It was a black dog."
Upon hearing his answer, Sherlock stood up from the ground abruptly.
"A black, very large dog?"
Lupin noticed Sherlock's unusual behaviour. He looked up, seeming to have guessed something as well, and stared blankly at Sherlock.
"Yes, he was very large, reaching up to an adult's waist."
Sherlock slammed his fist into his palm.
"So it was him!"
"You've already seen him?" Lupin asked nervously.
"Not only have I seen him, but he also did me a huge favour!"
Sherlock did not specify what favour he meant. He paced back and forth in the Shrieking Shack, as though thinking something through.
"But that shouldn't be right. Without you telling anyone, no one knew he was an Animagus. It was easy for him to sneak into Hogwarts, and he even managed to sneak into the Gryffindor Common Room twice. Why was Harry never attacked? Was Harry simply lucky?"
He muttered to himself. Lupin heard him, but he also didn't know why that was the case.
Sherlock suddenly stopped pacing, stared at Lupin, and began analysing it step by step.
"The first time I saw him was just after school started at Hogwarts. At that time, he should have just arrived in Hogsmeade and hadn't found the right opportunity to sneak into Hogwarts. The second time was also at Hogwarts, on the evening of the first day of term. He was still staying in Hogsmeade, which means he still hadn't found an opportunity."
"By Halloween, I went to Hogsmeade again, but Black was no longer there. That night, while the Halloween feast was in progress, he violently broke into the Gryffindor Common Room. That means he had successfully entered Hogwarts before Halloween."
"And the third time I saw him was when the Dementors broke into the school Quidditch match. He was on the highest tier of the Quidditch stands. He must have thought no one would be there, but he happened to run into me!"
He paused suddenly.
The Shrieking Shack was exceptionally quiet, so quiet that Lupin's heavy breathing was unmistakably clear.
"This proves one thing," Sherlock said slowly.
Lupin stared at him and immediately asked,
"Proves what?"
"From the first time he broke into the Gryffindor Common Room on Halloween, to when I met him during the Quidditch match, and then to the second break-in a few days ago, throughout that entire period, he never left Hogwarts!"
Lupin, however, did not quite agree with Sherlock's conclusion.
"Impossible. I have used the Marauder's Map, and I have never seen his name anywhere in Hogwarts."
Sherlock stared into his eyes.
"Does the Marauder's Map really cover the entire Hogwarts grounds?"
Lupin answered without hesitation.
"Of course!"
"What about the Forbidden Forest?"
Lupin froze.
Yes.
The Forbidden Forest was vast. As one of the creators of the Marauder's Map, Lupin knew very well that they had recorded every corner of Hogwarts, every secret passage, and every exit.
But the Forbidden Forest could not possibly be included because it was simply too large.
If Black wanted to find a place to hide within the Hogwarts grounds, then the Forbidden Forest would be the ideal hiding place.
"That's right! He could be hiding in the Forbidden Forest!"
A look of astonishment appeared on Lupin's wolfish face. He now only felt that Sherlock's former boss at the Auror Office had been a complete idiot.
To let someone with such talent go was definitely one of the Ministry of Magic's greatest losses.
"We'll go and find Dumbledore tomorrow, tell him everything, and then conduct a thorough search of the Forbidden Forest!" Lupin said excitedly.
Sherlock did not respond to his proposal but instead looked at Lupin with bright eyes.
"Perhaps we can try tonight."
Lupin was shocked by Sherlock's words.
"Tonight? Just us?"
"Yes, tonight. Just us," he said firmly.
"But I'm still in my Werewolf form..."
"That's exactly what I need—your Werewolf form." Sherlock looked at him and said, "In this state, aren't your hearing, sense of smell, and vision far sharper than normal?"
Lupin replied hesitantly,
"...That's true, but with just the two of us, searching such a vast Forbidden Forest..."
"I know the chances are slim, but it's definitely worth trying."
In the end, Lupin was persuaded.
The two of them returned to the Whomping Willow through the tunnel leading from the Shrieking Shack. By then, it was almost one o'clock in the morning. Apart from the chirping of insects and birds from the Forbidden Forest, there was no other sound.
Sherlock and Lupin did not split up because, even if they searched separately, it would be completely useless in such an enormous forest.
By staying together, they could ensure that if they found Black, he would not escape easily.
After entering the Forbidden Forest, they searched deeper inside. In his Werewolf form, Lupin was undoubtedly one of the magical creatures at the very top of the food chain in the Wizarding World. The Ministry of Magic's official danger rating for Werewolves is XXXXX, on par with creatures such as Dragons and Basilisks.
Therefore, they did not need to worry about being attacked by other magical creatures in the Forbidden Forest; with Lupin there, they all kept their distance.
Sherlock and Lupin walked deep into the forest for about an hour, even reaching the former territory of the Acromantulas, an area that had now been burned into barren land, yet they still saw no sign of Black.
"It won't work. With just the two of us, it's very difficult to find a black dog in such a huge place." Lupin shook his head. He felt this trip was destined to end in failure.
Sherlock, however, stroked his chin thoughtfully.
"Perhaps we're searching in the wrong direction. We subconsciously assumed that since Black wanted to hide in the Forbidden Forest, the deeper he hid, the safer he would be."
"But in fact, in his Animagus form, it doesn't matter where he hides in the Forbidden Forest because, apart from you, no one knows his Animagus form. Even if someone saw him in the forest, they would simply see a black dog and think nothing of it."
"Furthermore, he has to keep an eye on what's happening at Hogwarts. If he hides deep in the Forbidden Forest, it wouldn't be convenient for him to observe the school."
"So we shouldn't be searching deep in the forest; we should be searching along the edge of the Forbidden Forest closest to Hogwarts."
Lupin was amazed by Sherlock's reasoning.
Wizards, especially pure-blood Wizards, had always been naturally disadvantaged when it came to logical reasoning.
Most magic requires strong emotions to cast, so generally speaking, the longer someone studies magic, the harder it becomes for them to maintain a truly rational state.
Yet Sherlock's performance at that moment was completely abnormal by Wizarding standards, piecing together every clue and deducing a conclusion that came astonishingly close to the truth.
They immediately turned back and began searching along the edge of the Forbidden Forest instead.
But after searching for another hour or so, as the eastern horizon gradually turned pale, they still found nothing.
Sherlock shook his head and sighed.
"It seems the two of us can't find him on our own. Let's return to the Castle, tell Dumbledore everything, and then get more people to search for him."
Just as Sherlock finished speaking, Lupin suddenly pricked up his ears.
"Wait!"