"It's likely the Weasley twins' handiwork," surmised Lupin. "Since Harry can't go to Hogsmeade this year, they gave him this map."
Lupin conjectured clearly. He rose from his chair, slipped on his coat, and prepared to depart. Sherlock, on the other hand, was transfixed by the Marauder's Map, absorbed in contemplation. "Since the Marauder's Map shows the location of everyone in the castle it should also show Sirius Black. Why don't we use it to track him down?"
Lupin disagreed with a shake of his head. "Hogwarts is enormous, and the map holds a wealth of information. Moreover, even if we manage to spot Black on the map the instant he sneaks into Hogwarts, who at the school would have the resources to constantly monitor it?"
While his argument was sound, Sherlock couldn't help but sense that there was more behind Lupin's nonchalant dismissal of the idea. Nonetheless, without further questioning, he simply nodded and accompanied Lupin out of the castle. The moon had already risen, suspended in the sky and casting a brilliant white glow. Lupin's demeanor hadn't changed notably, but his face bore an unusual pallor under the moonlight. Sherlock noticed this alteration and inquired, "Do you not experience other symptoms before transforming?"
Apart from the pale color of his face, Lupin's emotional and mental states seemed relatively normal. He elucidated, "As the time for transformation nears my body begins to feel more depleted. The physical fatigue prevents me from casting many high-level spells, or sustaining spellcasting for prolonged periods."
Sherlock empathized with Lupin's situation. In their world, wizards didn't have a mana bar as in video games. Their magic strength represented their magical power; the stronger their magic, the more powerful their spells, as opposed to it being a depletable resource. If these qualities were to be equated with anything, it would be endurance. Continuous spellcasting left wizards physically exhausted, with their stamina quickly waning.
Student wizards practicing spells usually faced minimal restrictions; when tired, they could rest for a bit and then continue. Hypothetically, as long as a wizard maintained sufficient physical fitness, they could cast an unlimited amount of spells. This was why Sherlock insisted on exercising every morning, to keep his fitness up. His Floating Wand Casting System was rather physically taxing, even for him. Casting spells with two hundred and one wands at once would leave him depleted after three uses. He could barely manage a fourth, and by the fifth, he'd collapse from exhaustion.
Even after reduction of spells, under typical spellcasting conditions, Sherlock could release between five hundred to six hundred spells in a row before being thoroughly depleted. During their physical development phase, Hogwarts students who were lax with their exercise routines would feel tired after casting around a hundred spells, and completely exhausted after two hundred. But given the intensity of education at Hogwarts, the likelihood of students practicing a hundred spells a day was rare. Therefore, studying magic appeared limitless to these students.
Furthermore, during traditional wizards' duels, typically ten spells were enough to determine the victor, so it was highly unlikely for two opponents to persistently cast two to three hundred spells without a conclusive outcome. Consequently, in this world, there was no concept of 'mana'; as long as you had the ability, you could cast spells at will. This held true for everyone except anomalies like Sherlock who could unleash two hundred spells at once. Sherlock continually studied the reasonable combination of the number of spells cast with a wand. Upon facing Fiddlesticks the previous time, casting two hundred Patronus spells was clearly excessive.
Even with a reduction to a hundred spells, and using a sensible combination, the same effect could be obtained. While directing two hundred laser rainbows all over the sky might produce a strong deterrent effect, what was consumed was Sherlock's stamina.
Lupin led Sherlock to the Whomping Willow, standing at the edge of the Forbidden Forest. The willow was unpredictable and hostile; ordinary people couldn't get close to it. When they were approximately ten metres away from the tree, Lupin swiftly pointed his wand at a small stone at his feet. The stone instantly transfigured into a squeaking mouse, which scurried off and leapt onto the trunk of the Whomping Willow. It seemed to have made contact with a scar on the tree trunk, and the violent magical willow immediately went still. Lupin then led Sherlock to an entrance to a tunnel beside the tree, and they crawled in together.
"Dumbledore planted this Whomping Willow the year I joined school," Lupin narrated to Sherlock, his voice thick with nostalgia and a hint of repressed sadness, "He even prepared this secret tunnel specifically for me. Each month, when the time for transformation drew near, he would arrange for Madame Pomfrey to escort me here. From this secret passage, I would make my way to the Shrieking Shack in Hogsmeade to endure my transformation to a werewolf, ensuring I wouldn't harm anyone." However much Lupin strived to mask it, Sherlock could discern the sense of loneliness echoing in his voice.
Sherlock Forester refrained from further probing. Everyone harbored their own little secrets, and he was no exception to this unwritten rule. They had been traversing the darkened pathway for nearly half an hour before they found themselves at the doorstep of a ramshackle, filth-covered shack. They were now in Hogsmeade, home to the most dreaded dwelling in the entire magical world of Britain - the Shrieking Shack.
Sherlock's gaze swept over the decrepit structure and instantly brought to mind scurrilous tales of this haunted manor. With an air of certainty, he conjectured, "This place earned its moniker 'The Shrieking Shack' because of the unidentifiable screams heard here at night; were these remnants of your transformation during your school years?" His question hung in the air.
Professor Lupin nodded in confirmation. "True indeed, Dumbledore envisaged these rumors in order to deter anybody from venturing inside during my transformation."
Forester blinked pensively then asked, "And there was a close call once, wasn't there?" Lupin gazed back at him in startlement, "You...know about that?"
"It was Snape who told me about it himself," Forester responded with a sigh. "He unveiled the incident to me when I asked why he harbored such resentment towards you. He said that during one of your transformations, your friends led him right to the shack; apparently you nearly killed him in your werewolf form."
Lupin fell into a loaded silence, his melancholic gaze revealing he was gripped by a regretful memory from his past. "We were incredibly reckless at that time, Sirius most of all."
The utterance of this familiar name caught Forester's attention causing him to momentarily suspend his train of thought, before understanding dawned upon him.
Sherlock threw a questioning look at Lupin. "Did you say Sirius? As in Sirius Black?"
An almost imperceptible nod confirmed his guess. Lupin seemed to regret letting the name slip, but did not express any real concern about revealing the secret. However, mid-sentence, his expression twisted in agony, "Wait, we'll continue this conversation later, Sherlock..."
Forester immediately recognized this bodily convulsion as the precursor to Lupin's transformation, simultaneously taking strides back to ensure sufficient distance for casting spells in an emergency while observing Lupin as he transitioned. A gut-wrenching cry echoed around them as Lupin's features began to distort.
His head lengthened, body elongated, shoulders hunched and fur sprouted on his face and expanse of his body, his fingers morphing into vicious claws. A grotesque blend of a man and wolf - a werewolf - replaced Lupin before Sherlock's eyes. With a furrowed brow and shrunken pupils, the creature had a more human look than an average wolf. After the transformation, Lupin, with his predatory eyes, looked at Sherlock, but his gaze held calmness instead of savagery, indicating the beneficial effect of the previously consumed Wolfsbane Potion.
Sherlock had accompanied Lupin to observe his transformation for academic purposes, but a new query now seized his mind, and he glared into Lupin's eyes seeking answers. "So you used to be friends with Black when you were a student?"
Lupin, completely covered in a matted grey-black fur, motioned for Sherlock to sit. They both ignored the grit and grime of the Shrieking Shack sitting directly on the cold, dusty floor. "I heard that you joined the Order last year," Lupin's gruff voice in his werewolf state still held his characteristic gentleness.
"So even if I try to hide something from you now, you'll eventually come to know the truth."
Sherlock remained silent, attentively listening to Lupin's account of his past. "Albus Dumbledore has always been a benevolent headmaster - he let me study at Hogwarts despite knowing that I was infected. I didn't just attain magical abilities here but also formed some invaluable friendships."
"When I first made friends I was terrified of what might happen should they find out about my sickness, yet unbeknownst to me they figured it out almost immediately."
"However, even knowing about my werewolf condition did not disrupt our bond. They included me as though nothing changed and even learned powerful transformation magic to accompany me during my transformation."
Sherlock, upon hearing this, narrowed down the probable identities of Lupin's Hogwarts friends. "You're referring to Sirius Black and James Potter, aren't you?"
Lupin looked surprised. "How do you know about James?"
Sherlock explained, "Mr. Weasley informed me at the start of this year about Black's betrayal of Harry's father. They were apparently best friends once. If Sirius Black was your friend too, I deduced, it would naturally follow that James Potter was also among your friends."
Lupin nodded, his eyes carried a grim pain. "Sirius, James and Wormtail... we were inseparable."
Sherlock quirked a brow, "Wormtail… Peter?" The name seemed familiar; Sherlock had heard it mentioned by Mr. Weasley at the Leaky Cauldron, yet, a distinct memory remained just out of grasp.
Lupin's voice grew heavier. "Yes, Wormtail, that's Peter Pettigrew. We were a tight-knit group back then. I'm sure you're aware of the ensuing catastrophe. Sirius betrayed James, leading to his and Lily's demise. Peter later retaliated to avenge their death, only to be blown apart by Black's spell, leaving behind nothing more than a single finger!"