Harry Potter: A Certain Ancient Rune Professor of Hogwarts (TL)

The next day, Felix arrived at the corridor where the attack had happened last night and isn't surprised to encounter Filch.

The corridor had obviously been cleaned by him, and the puddles of water had disappeared from the floor. On the wall with the words "Chamber of Secrets has been opened," he laid on an empty chair.

At the moment, his back is turned from Felix, and he's painstakingly scrubbing the words on the wall with cleaner, but it seemed to be futile.

"Mr. Filch."

Filch turned back, his eyes protruding, his face plastered with an unnatural flush and his mouth muttering, but when he saw Felix, he greeted him politely, "Professor Hap."

"I've come to look at the scene, maybe I can find some clues left behind."

Felix hadn't dealt much with the Filch when he was at school, back then he didn't have Mrs Norris as a helper, while he himself was completely immune to him with his excellent Disillusionment Charm.

Filch gave way and stood somewhat limply on one side. He had revealed himself as a Squib yesterday, and today he didn't want to stay a second longer in the face of this genius professor.

"Well, then, I'll leave you to it, Professor, I have a little more ... to do."

"Go ahead and get busy," Felix responded, "Oh, right." He waved his wand and the writing on the wall faded all at once.

"Huh?"

He is a little surprised and quickly moved over to the wall, looking the writing up and down. "It seems to be an obligatory spell, but it's not a permanent adhesive spell." Felix gestured at the wall with his wand, and soon the writing disappeared.

"Thanks, thanks." Filch turned red, said hastily, and left quickly, without taking even his cleaning kit with him.

Felix began to search the surrounding area, and soon, he found a clue.

He crouched down and tapped his wand on the ring on his left hand, and a large magnifying glass appeared in his hand.

Felix looked closely at the floor, where there is a burn mark.

"What is this? How did it appear?"

Felix looked at the girls' lavatory which is directly across the hall and without much thought he quickly pushed open the brass handle and stepped inside.

It is a rather dark, damp place, the walls were stained, the floor is full of puddles of water, the tiles on the row of sinks were peeling off, and the only source of light is a few dark candles.

Fighting back the discomfort, Felix's eyes darted around.

From the innermost cubicle came a sudden voice, "Who's there?" With that, a grim-faced spirit rushed out, her pearl-coloured glasses covering most of her face.

She looked over at Felix, clearly recognizing this professor.

Dazed and somewhat disbelieving, the spirit glanced behind her, and yes, this is her own personal basement, the girls' lavatory ...

" Professor, prof...?"

"Hello, Myrtle." Felix's voice is rather calm. He is here to investigate a case, he had a legitimate excuse, well, that's all.

Myrtle looked at him blankly for a few seconds, then suddenly let out a scream and the whole spirit flew back into the Flush Toilet, he could even hear a loud, crisp splash.

Felix: "..." As far as everything goes? There's a question I wanted to ask her, and I can force myself not to be embarrassed for that.

Felix said, "Myrtle, I know you're here, did you see that attack yesterday ..."

"No! Nothing!" Myrtle yelled from the cubicle.

With that, he heard footsteps some distance away, and with a frightened heart, he hurriedly cast a Disillusionment Charm on himself and quickly left the lavatory, brushing past a red-headed girl.

Being spotted by a spirit isn't terrible, but if a student ran into him ...

His whole reputation would be ruined.

Over the next few days, he cooperated with several professors when he was not in class and searched the entire castle, with the uncoloured result that he found nothing.

One day in the great hall, Felix is still thinking about it as he ate his lunch.

"It all started with the Dark Lord's Horcrux but knowing that doesn't seem to help ... I don't know who the heir is, where the Chamber of Secrets is, and where the Horcrux is hidden."

"Chamber, Slytherin, heir, petrified ... those are obviously the keywords. But how do you connect them?"

Felix always felt like he is getting very close to the truth, but yet he just separated by a fog.

"Slytherin ... snake?"

He tried to remember, trying to lift the dusty memories that had been sealed away for so long. He seemed to remember seeing something, "Harry" fighting a gigantic snake. But the memory is rather vague, and he wasn't sure if he is remembering it correctly; he is under the impression that "Harry" had also taken out a large group of dementors by himself.

How is that possible? Even a normal adult wizard couldn't do that!

Besides, how could Dementors attack the school?

But Felix quickly warned himself that in the world of fiction, anything is possible. Especially with the presence of a 'protagonist'.

"So, it's probably true that a giant snake caused Mrs. Norris's petrification." Felix went along with this conjecture.

But once again, he had a problem.

What snake had the power to petrify?

All Felix could think of is Medusa, but that magical creature was extinct.

"Don't rule out that Slytherin performed a bloodline graft ... from his surviving notes, he was very deep into bloodline research."

He hadn't made up his mind until he finished his lunch. He soon had a new idea, though, gathering rumours about the Chamber of Secrets from Hogwarts over the years and sifting through them one by one.

Perhaps the truth is hidden amongst the rumours.

...

Three days later, Felix stood across a tapestry of "Trolls Beating Up Barnabas" on the seventh floor of the castle, watching oddly as a silver door slowly appeared.

And there you have it, he found it?

With a little hesitation, he tapped his wand against his chest, and a light flickered across his wrist, ankle, and chest, and then he stepped inside.

It's an oversized junk storage room, with mountains of various discarded items, broken quill pens, old books, damaged Sneakoscopes... He also saw the golden Snitch with half of its wings missing.

He walked around carefully and found a trace of no one.

"A hidden room?" He could hardly imagine that the proud Slytherin would have placed his secret room here.

"This room is quite hidden, though. It must have some interesting enchantments to study and research for another day." Felix walked out of the room, looking somewhat fondly at the silver door that had quietly disappeared.

On the other side -

The trio also working hard to discover the secrets of the Chamber of Secrets, and by "working hard" I mean mostly Hermione Granger.

After days of fruitless searching and a two-week rental list on Hogwarts History of a Pastime, the Gryffindor witch finally raised her hand to ask a question in History of Magic class for the benefit of the group and gained valuable information about the Chamber of Secrets.

Poor Professor Binns had to go off the curriculum and lecture on 'myths and legends' while the crowd peered at him, much to his annoyance. After this interlude, his slow, dry voice picked up speed - making his lessons even more hypnotic than ever before.

The young wizards, who had been in high spirits, once again collapsed, their faces rapidly becoming blank and dazed.