Sherlock Apparated directly to Diagon Alley.
A week ago, he had learned that Harry was staying in a room at the Leaky Cauldron; he only found out what had happened after Harry sent Hedwig to deliver a letter to him.
After retrieving his wand from Ollivander's, Sherlock headed to the Leaky Cauldron to visit Harry, who had been staying there for nearly a month.
"...I really thought I was going to be expelled at the time, but the Minister actually said, 'We don't expel students for blowing up their aunts like balloons with magic.'"
As Harry spoke to Sherlock about this, his face was still filled with disbelief.
"I thought he was a very easygoing person, but when I asked him to help sign my Hogsmeade weekend permission form, he wouldn't agree, saying I'm only safest at school."
Since arriving in this world, Sherlock had not yet seen the true face of Minister for Magic Fudge even once.
But that didn't stop him from knowing through various channels that Fudge was a very politically cautious man.
Everything he did seemed to be preceded by a consideration of whether it would shake his position as Minister.
Just like how he didn't hold Harry responsible for performing magic outside of school, especially on a Muggle.
Now everyone in the Wizarding World knew that Black had escaped from Azkaban, and they were all concerned about Harry Potter's safety.
If anything happened to Harry in the current situation, Fudge would face intense pressure from public opinion.
"The night you ran away was indeed very unfortunate," Sherlock recalled. "I was out on some business at the time and wasn't home."
He didn't lecture Harry about it.
To reach that point, Harry must have been pushed to his limit.
Otherwise, he would have exploded long ago, so Sherlock didn't bother with nonsense like saying he shouldn't have run away alone.
"It's alright, Professor," Harry said, shaking his head. "I've felt pretty good living at the Leaky Cauldron these past two weeks. Now Ron's family is staying here too, along with Hermione. Tomorrow we'll go to Platform Nine and Three-Quarters together to catch the train to school."
After Sherlock and Harry chatted for a while, Mr. Weasley called him alone to a corner of the Leaky Cauldron lobby, intending to speak with him privately about a few things.
"I heard from Kingsley that after a school year as the Defence Against the Dark Arts professor at Hogwarts, you've changed a lot."
Without discussing anything else, Mr. Weasley looked Sherlock up and down with a surprised gaze as soon as he saw him.
"I heard from the children about what happened at Hogwarts at the end of last term. Molly and I were both worried sick for you, Sherlock."
Sherlock said with a smile,
"Although the process was a bit thrilling, I think having such a result is a good thing; at least I can think more clearly about some matters now."
"Yes, we're all very happy you think that way—or rather, we've all been waiting for this day for a long time," Mr. Weasley said with great relief.
They only chatted briefly about that before Mr. Weasley shifted the conversation to the main topic.
"You should already know about Black escaping from Azkaban," he said in a heavy voice.
Sherlock nodded.
"Back in July, I was travelling in France with Harry when I received a letter from the Ministry of Magic, asking me to return Harry to his aunt's house as soon as possible. I knew then that this matter had a lot to do with Harry; Black escaped from Azkaban wanting to find Harry to avenge his master."
Mr. Weasley deliberately lowered his voice.
"It's not that simple, Sherlock. You must keep a close eye on Harry at Hogwarts. You must absolutely not let him go looking for Black on his own!"
Sherlock's expression suddenly became very surprised.
He looked around to ensure no one was paying attention to his conversation with Mr. Weasley; he knew that what followed must be a secret known to very few people.
Mr. Weasley's face became gloomy and pained.
"Sirius Black—before the Potter family met their end, he was actually Harry's father James's best friend. When Harry was born, he was even invited to be Harry's godfather."
Sherlock held his breath and continued to listen to Mr. Weasley.
"At the time, there was a prophecy that a saviour would defeat You-Know-Who, which was already circulating everywhere in the Wizarding World. Harry's birth perfectly met all the conditions of the prophecy, so everyone advised James and his family to go into hiding as soon as possible."(TN: How does he know?)
"And they did. James and his close friends used a powerful spell—the Fidelius Charm. They told their hiding place's address to only one person. If the Secret-Keeper never spoke the address, even if James's family were hiding right under You-Know-Who's nose, he would never find them."
"But anyone close to James could guess who he would choose as his Secret-Keeper: only his best friend, Sirius Black!"
"Then came the tragedy where You-Know-Who found James's family. And as for why You-Know-Who found them, there is only one possibility: the Secret-Keeper James trusted most leaked the secret."
"It was also on that day that James's other friend, Peter Pettigrew, specifically went to find Black to confront him about why he betrayed James. Then Black used an extremely powerful Blasting Curse, blowing Peter up until only a finger remained, and a dozen Muggles died because of it!"
"Finally, Black was caught. He didn't deny any of his crimes. There wasn't even a trial by the Wizengamot; the charges were established, and he was directly sentenced to life imprisonment in Azkaban."
Sherlock heard the entire story of those years from Mr. Weasley.
He finally understood why Mr. Weasley wanted him to watch Harry and not let him go looking for Black privately.
If Harry knew the whole story, given his personality, he probably would do such a thing.
To find Black and avenge his parents!
Mr. Weasley looked grave.
"So, if possible, you must keep an eye on Harry at school. Black is very likely to take the initiative to let him know about this and then provoke Harry into coming to find him."
Sherlock also promised with a serious expression.
"I understand. I'll do my best to watch Harry at Hogwarts and keep him from doing anything adventurous."
"It's for the best with you watching him," Mr. Weasley nodded.
Sherlock sat at the Leaky Cauldron for a while longer, chatting with Mr. Weasley about the currently chaotic situation in the British Wizarding World, before leaving and returning home.
Sherlock didn't take these old stories told by Mr. Weasley entirely at face value.
He always felt that this story wouldn't be so simple; there would surely be some twist, just as he still wasn't certain whether the one who turned into a rat and escaped was actually Black.
But regardless of which direction the story ultimately took, continuously improving his own strength was certainly not a mistake.
While obtaining fifty wands from Ollivander's, Sherlock also used legal and proper channels to buy a bag enchanted with a reinforced Undetectable Extension Charm to serve as a container for his usual stock of wands.
That very night, he returned to the place where he had previously experimented with the Blasting Curse. He spread out all fifty-one wands, each one floating in mid-air under the control of his Control Magic.
Controlling such a number of wands certainly couldn't reach a proficient level in one go; Sherlock had to practise diligently to achieve precise control over every single wand.
As it was now, his attempt to move just one of the fifty-one wands was very stiff, often resulting in four or five wands moving together.
There were no shortcuts for this kind of thing; only through more practice could he become proficient.
Afterwards, he continuously attempted to cast spells like Petrificus Totalus and Stupefy. Just as he had estimated before, no problems occurred.
However, when casting spells, the fifty-one wands could only complete the casting of one type of magic at the same time.
The key to magic casting still lay in the wizard's mental conception of the spell. He couldn't determine the petrification effect of Petrificus Totalus while simultaneously disarming an enemy; after all, Sherlock only had one mind.
If he tried to force it, the final result would only be that neither spell would be cast.
Sherlock had only made an attempt. If he could truly manage to cast different magics simultaneously by himself, he would genuinely be able to walk tall in the Wizarding World. The number of wands one person could control would be equivalent to a wizarding army of that size.
Sherlock didn't dare to try spells like the Patronus Charm and the Blasting Curse here.
With fifty-one wands casting such spells together, the commotion created would be far too great.
If he tried, someone nearby would likely call the police, claiming supernatural phenomena were occurring or that two armies were fighting.
As long as he confirmed that he could successfully use the spell with one wand using Control Magic, then fifty-one wands would likewise have no issues.
After finishing the experiment, Sherlock returned home and spent his last night of the holiday there.
Then, the next morning, after packing some common daily necessities and clothes, Sherlock Apparated directly to Hogsmeade.
The landing point he chose was the same alley he had returned to from the Apparition remedial class before.
After walking out of there, Sherlock felt something was wrong.
The streets of Hogsmeade were a bit too quiet.
Looking around, there wasn't even a single pedestrian.
As the only wizarding village in all of Britain, even without Hogwarts students around, there were usually plenty of tourists coming here daily to relax.
But now, looking down the main road of Hogsmeade, it seemed to have become a ghost town, with not a soul in sight.
Just as Sherlock was frowning at the strange situation before him, a three-person Auror patrol happened to appear from around a corner, and they spotted Sherlock as well.
"Sorry, sir, please don't move around. Stay where you are and cooperate with our inspection."
The three Aurors immediately walked up to Sherlock, each holding a wand and remaining in a constant state of alert.
Sherlock didn't do anything to show dissatisfaction, instead cooperating with their investigation.
"We want to know your name and the reason for your visit to Hogsmeade."
"Sherlock Cavendish, Defence Against the Dark Arts professor at Hogwarts, heading to Hogwarts from Hogsmeade."
One of the Aurors, clearly the captain of the squad, looked up and carefully scanned Sherlock's face.
"Yes, I've seen your photo in the newspaper, Mr. Cavendish. Alright, you can head to Hogwarts as soon as possible; try not to linger in Hogsmeade for long."
Sherlock frowned and looked at them, asking,
"What happened?"
The Auror captain didn't intend to keep it from him.
"There was an attack last night. Johnson, the owner of Scrivenshaft's Quill Shop, was attacked. The matter is very serious, and added to the recent business with Black, Hogsmeade is now under full martial law. Dementors will also be stationed here soon; they want to catch Black here. A heap of trouble has appeared in this town. If it's not necessary, try not to come here again until things are resolved."
He spoke with a headache, then prepared to leave with the other two Aurors to continue patrolling elsewhere.
Sherlock suddenly asked them again,
"Is the attacked owner in a state that looks like they've been given the Dementor's Kiss?"
The three Aurors suddenly stopped in their tracks. The Auror captain who had just spoken with him turned his head back with a serious expression and stared at him.
"How do you know that?"
"Don't be nervous. Kingsley Shacklebolt from your department is my friend; I helped out when a similar case occurred some time ago."
Hearing him say this, the Auror captain's expression relaxed slightly.
"But wasn't it said at the time that this matter was taken over by Aurors from Germany? Why are attacks still happening?" Sherlock asked.
Knowing that he was aware of some inside information, the Auror captain shook his head helplessly and grumbled.
"This case has indeed been handed over to those three wizards from Germany. They do have some skill; they predicted in advance that the culprit's next move would be near Hogwarts. But the attack still happened, and we have to handle the aftermath. Director Scrimgeour has also given those three German wizards an ultimatum, demanding they catch the culprit before the next attack occurs, or else he will lodge a protest with the German Ministry of Magic."
Lodge a protest... Sherlock could hear how helpless Scrimgeour was from those words.
Regarding the culprit committing crimes within British territory, they had no clues at all, and they had to invest the vast majority of their manpower into the manhunt for Black.
Even if another attack occurred later, he wouldn't dare kick those three German Aurors out because there would be no one left to take over the case.
The British Aurors were now facing a very embarrassing situation, and Scrimgeour was under immense pressure.