As Sherlock Forester focused on the last sentence in the notebook, a profound silence befell him. The words were unmistakably inscribed by Sally Forester, late mother to the previous owner and written impeccably in her own hand, likely penned just before her tragic passing. It was palpable that during this period she had still preserved her mental faculties and what happened following the deeds outlined in this note had driven her to insanity. Swiftly, Sherlock gathered the journal positioned on the table and delved into the first page with attentiveness.
"Looking at Sherlock at this moment," Sally had started as if recording entries in a personal diary, "I feel that he is a joint testament to Victor's and my existence. Parenthood fills a woman with indescribable joy, and despite my rationality, unreasonable joy surrounds me, even now."
"As I have tended to my newborn Sherlock these past days, my mind floods with memories of my torment under the Cruciatus Curse, which cruelly fragmented my soul."
"To build a spell that could mend a soul, I had to immerse myself into comprehensive research on the subject. Although my work was hindered by the absent 'thread' material, my studies have placed me at the forefront of the magical community in terms of understanding of the soul."
"The more knowledge one acquires, the more humbling it is to realize the vast stretch of what remains unknown. The soul is a remarkable and complex matter. In spite of the lack of extensive research on the soul in magic, every spell is fundamentally linked to the soul."
"Sherlock's birth has rekindled my interest in this area of study. I am convinced that the soul, with its enormous might, can provide Sherlock with a protective charm of sorts. I want to create something that, in my eventual absence, will continue to safeguard him."
The next pages detailed how Sally helped construct her own underground study in her home, where every book she acquired over the years on the subject of the soul was stored. This marked the continuation of her research on soul magic.
Every magical experiment requires a subject, Sally willingly chose herself. Her soul already lay shattered, yet she boldly embarked on the perilous journey of performing various volatile magic experiments on her soul. Her objective was to develop a spell using the power of the soul that could shield another's soul from harm.
In the magical world, spells are intricately tied to emotion. To cast the Petrification spell, one needs to harbor an intense desire to petrify the opponent. To perform the Disillusionment Charm, one must believe wholeheartedly they will completely disappear from view. To cast the Killing Curse, one must embrace their darkest thoughts and form a resolute intent to kill. These emotions must be genuinely felt and exhibited by wizards, which is likely why wizards are often perceived as lacking rational and logical thought. Their sensitivity becomes their habit and maintaining an objective outlook could actually hinder their magical capabilities.
Sherlock spent some time musing over this. Where did all these emotions originate? The physical body was essential to life, but if a person lost all desire and emotion, even if physically alive, they would essentially become indistinguishable from the dead. An ordeal reminiscent of the Dementor's Kiss, a tactical attack that would suck all happiness out of a wizard, leaving them as a lifeless shell despite their still-beating heart. The soul, he decided, was the answer.
Building on this, Sally hypothesized that all magic, hidden or otherwise, was interconnected with the soul. Since magic was projected by the soul onto the external world, logically, the soul should have the ability to negate those effects. Killing Curses, particularly, targeted the soul directly. The three Unforgivable Curses, of which the Killing Curse was one, were the most pervasive spells known to the magical community with no clear way to counter them. The other two, the Cruciatus Curse and the Imperius Curse weren't innately fatal, but the Killing Curse could be seen as the bane of existence itself. It directly impacted the soul of its target and the recipient died instantaneously with no visible damage. Yet, there was no spell in existence that could withstand or counter the Killing Curse.
If Sally's plan were to succeed, soul-protection magic might be capable of resisting the effects of the Killing Curse! Her meticulous experiments involved using rabbits and mice, their insignificant souls serving the purpose of preliminary testing. As a proficient witch, Sally developed a rudimentary method of soul-protection magic after numerous trials.
One conclusion that piqued Sherlock's interest was: "Rabbit A132 managed to survive, which unveils the feasibility of my research."
Disappointingly, another entry read: "Rabbit B341, who played the part of Rabbit A132's protector, perished. So essentially, the protective spell does nothing more than trade one life for another."
Conversely, Sally also observed a recoil when the Killing Curse targeted the protected rabbits, reminding her of the Shield Charm. Furthermore, the survivors seemed to develop a form of magical resistance which she stored as significant data for future reference.
Propelled by her findings, Sally refined her soul-protection magic then shifted to human trials. Still working alone, she chose her own soul to experiment on. The effectiveness of the spell in warding off or reflecting the Killing Curse was already validated in her animal trials, hence her shift in subjects didn't pose a lethal threat. After extensive trials, Sally discovered that successful casting of this potent soul-protection magic required stipulation. The caster must experience a potent positive emotion towards the individual being sheltered – love, she realized. The magic wouldn't work without intense feelings of parental, maternal, platonic or romantic love. Furthermore, if successfully cast, the souls of the protector and protected would intertwine, ensuring the magic persisted regardless of whether the protector remained alive. This could be explained by the fact that in the world magic, souls didn't always dissipate after a person's death, which is what enabled the existence of ghosts.
Even death as a result of the Killing curse didn't annihilate the soul; rather, it caught the soul and incarcerated it within the psyche of the perpetrator. Consequently, providing the Soul Protection Charm was cast successfully, even the death of the protector wouldn't abate the spell. Upon mastering this magic, Sally tethered her soul to Sherlock's, executing a soul-binding contract. This was her parting gift to the person she birthed. Once this spell was assimilated, she stepped away from Sherlock's life, only to resurface in bouts of insanity. Sherlock was flooded with a mix of emotions upon perusing this experimental diary. The original owner's mother, Sally, was indeed admirable. Despite her divorce from conventional maternal roles, she'd exerted her utmost to safeguard the original owner. Yet ironically, the original owner's life abruptly concluded not from a magic-wielding antagonist, but a self-inflicted daredevil magic experiment. Sally's method of protection could safeguard the soul, but the original owner died from physical injuries - which her charm couldn't prevent.
Then the new Sherlock arrived, took up residence in this body, causing the charm to believe the original owner's soul was damaged, causing it to split. Shortly after, he discovered the book, "Soul Stitching" concealed in the restricted section of the Hogwarts library. Sherlock's soul from a parallel reality fused with the comatose soul of the original owner, stitched together by the threads of Riddle's horcrux, rendering Sherlock and the original owner indistinguishable. The protector charm initially woven by Sally was now reactivated to guard Sherlock as well.
Sherlock lingered there, steeped in silence, the diary open before him, before finally releasing a heavy sigh. An echo of recollection struck him. In his previous life, "Philosopher's Stone" was the only complete Harry Potter book he'd read, and a striking similarity betwixt Lily Potter's protective spell against Voldemort's Killing Curse and Sally's Soul Protection Charm startled him! He also recollected a scene when Dumbledore explained to Harry that the scar on his forehead symbolized his mother's love. Wasn't this the underlying requirement of the Protection Charm? It demanded the protector have an immense affection for the protected!
A wave of confusion swept over Sherlock who remained stock-still. Sally was the inventor and original researcher of this magic, yet how did Lily Potter come across it? There was no reference to Lily Evans in the diary. By the time this spell was pioneered, Lily must have been a first or second year student at Hogwarts, without access to such sophisticated magic. This perplexity caused Sherlock to scrutinize the diary once more and he paused at a paragraph that had previously escaped his attention.
"These are invaluable experimental data. After their collection, a copy could be archived in the Hogwarts library, just like the book on Soul Stitching."
When her experiment scaled such heights, Sally had deposited a back-up of her research in the Hogwarts library! Sherlock's face lit up with enlightenment. It was plausible that Lily chanced upon this spell in the Hogwarts library, learned it, and subsequently cast a soul-bound contract with Harry upon his birth! After Lily was struck by the Killing Curse and collapsed, Harry drew upon the might of the protective magic, rebounding Voldemort's spell, and survived that calamity, thereby becoming the boy who lived! It all made sense! No wonder when Sherlock asked Dumbledore, he was told that the mysterious scar was an emblem of his mother's love. The Protector Charm demanded love as its foundation, indeed, with its protection in place, even the the Killing Curse could be repelled!
Sherlock placed the experimented diary back in its original slot on the desk, abstaining from taking anything from the underground library. The room bore the imprints of a mother's love. Perhaps she was driven to lunacy for other reasons, maybe for someone else, and ended up berating and distrusting her own son. But despite her failure to perform her maternal duties in her later years, she still remained a paragon of a mother! As Sherlock mulled over the diary, Amy, perceiving the gravity of his mood, companionably maintained her silence, her gaze alternating between him and her surroundings.
Outside, twilight began to blanket the sky. The young Sherlock had returned home from school and his nanny had set about preparing his supper. Neither of them noticed the duo who had trespassed into the yard. Sherlock had locked all the doors again before descending to the underground office, leaving no indication of their presence. The library entrance was cunningly concealed amidst a thicket of shrubs in the garden, virtually invisible unless one ventured directly over it.
After thoroughly analyzing the diary, Sherlock emerged from the underground library with Amy. Casting a sidelong glance at the warm yellow lights from the house, he made no attempt to catch a glimpse of the ostensibly younger version of himself. Instead, he grasped Amy's hand and with a swift Apparition spell, whisked them both back to London. Their figures materialized abruptly in a secluded alley.
Sherlock stood there, adjusting his emotions before deciding to honor the promise he'd made to Amy regarding a hearty meal. They visited a Muggle restaurant Sherlock had previously visited in the company of Kingsley. It was one of the places Sherlock had been to before, but of course he couldn't sure that it had been open for 14 years until they had arrived. Luckily the restaurant seemed to have not been novel in 1991.
Amy's modest appetite did not mar her experience of eating out, especially with the dazzling view of London by night. After supper, they leisurely strolled across the London Bridge. Amy, armed with a vibrantly colored pinwheel, leaned against the railing, her golden locks dancing in the wind. Sherlock cast his gaze down at the River Thames, his heart awash with an influx of emotions.
What had seemed like a massive inconvenience to him just a few days ago was turning into a treasure trove of self-discovery. He turned his gaze to Amy, her face illuminated in the yellow glow of the sodium lights. Contentment permeated her features, yet her lips remained straight, as if unsure of how to form a smile. Sherlock reached out, lightly pinching her cheeks into a fleeting smile. "Life is a beautiful tapestry, Amy," he spoke softly, "It's woven with threads of love by those who cherish us and those we hold dear. So remember to smile more, it makes life so much better."