In the short time that Hermione had been away, another student had come to Sherlock's office.
Hermione knew the student; his name was Colin Creevey. He was a first-year Gryffindor student and a fervent admirer of Harry, constantly snapping photos, which had even begun to annoy Harry.
"Could I get a photo with you, Professor? I want to show my mum and dad when I go home for Christmas. Ever since I came to Hogwarts, they've been eager to know what the magic school is like. My little brother, Dennis, is also curious about where I'm studying, so I've been taking pictures all over the castle and getting photos with teachers and friends to show them."
Colin held up his camera and asked Sherlock.
Sherlock paused his work. He certainly wouldn't refuse such a request.
"Of course," he agreed.
Colin happily stood next to him, his shoulder level with Sherlock, who was sitting in his chair. Then, he aimed the camera at himself, a wide smile on his face, and pressed the shutter button.
"Thank you, Professor. I've collected photos with almost all the professors, except for Professor Snape. I plan to ask him tomorrow, hoping he'll agree."
Sherlock felt his chances were slim. He really didn't think Snape would agree to take a photo with anyone.
"Well, good luck tomorrow."
"Goodbye, Professor."
After waiting for Colin to leave, Hermione hesitantly entered Sherlock's office.
Sherlock looked at Hermione, who had come in empty-handed, and raised his eyebrows slightly.
"What's the matter, Miss Granger? Where's my book?"
Hermione tried her best to appear nervous, but in reality, she didn't need to act; she already looked nervous enough.
She stammered, "I—I'm sorry, Professor Cavendish. I kept the borrowing slip you gave me in my pocket, but when I got to the library, it was gone. I must have lost it on the way."
"Lost it?"
Sherlock looked at her and repeated the question.
"Yes, yes, Professor. I'm very sorry, but I was really careless, and I don't know when—"
Hermione hurriedly explained, but Sherlock interrupted her with a knowing smile.
"It's alright, Miss Granger. It's just a lost borrowing slip. I'm sure even if someone found it, they wouldn't use it for anything bad, right?"
Hermione was extremely nervous now. Even in the December weather, beads of sweat began to form on her forehead.
With her intelligence, she must have realized that Sherlock had already guessed something, but she continued to brazen it out.
"Of course no one would do anything bad, Professor."
Sherlock didn't press her further. He pulled out another piece of parchment, wrote a second borrowing slip, and handed it to Hermione.
"This slip won't get lost again, will it?"
Hermione immediately promised, "I swear, I'll have the book in your hands in ten minutes!"
"Go then."
After hearing Sherlock's words, Hermione grabbed the borrowing slip and fled from the office. Harry and Ron were waiting for her around the corner of the hallway and staircase.
"Well? Did Professor Cavendish find out?"
Hermione looked grave. "Although the professor didn't say it explicitly, I think he's already realized we tampered with his borrowing slip."
"Did he ask you why?" Ron asked anxiously.
"No. He wrote me another borrowing slip and told me to go to the library to borrow the book. You guys wait for me. I'll go get the book back for the professor and then find you."
Hermione ran quickly to the library.
After borrowing the book, she returned it to Sherlock and then reunited with Harry and Ron.
"At least the result is good."
Harry could tell that Hermione was upset, so he comforted her.
Hermione shook her head, blaming herself. "Professor Cavendish is such a good teacher, and I lied to him."
Ron tried to justify it. "We did it for Hogwarts."
"We have to apologize to Professor Cavendish after we investigate Malfoy," Hermione said firmly. "Regardless of whether Malfoy is the culprit or not, we should apologize to Professor Cavendish."
"We really should apologize to the professor," Harry agreed.
Ron looked at them and finally sighed. "Alright, since you've decided, I'll listen to you."
Hermione turned to Harry with dissatisfaction. "You even suspected him just because Professor Cavendish wished Justin good luck. I overheard the professor wishing Colin good luck for tomorrow outside the office. Let's see if anything happens to Colin tomorrow."
Harry scratched his head awkwardly. He also felt that his initial suspicion had been far-fetched. No matter what, Professor Cavendish didn't seem like the mastermind.
"Ahem, when should we borrow the book from the library?" he changed the subject.
"Tomorrow afternoon. We can't take two of the professor's slips to Madam Pince in such a short amount of time; she'll notice something's wrong."
The day passed quickly.
The next day, after lunch, Harry, Ron, and Hermione gathered at the entrance of the Great Hall.
"Let's borrow the book first, then go to class," Hermione said.
They walked together to the library. Harry handed the borrowing slip to Madam Pince, and they obtained the book they needed, Moste Potente Potions.
The process went very smoothly.
They went to an abandoned girls' bathroom on the first floor, hid inside, and found the recipe for Polyjuice Potion in the book.
The problem was that the potion recipe contained several ingredients they didn't have and couldn't find.
Ron looked dejected. "What are we going to do?"
Hermione pursed her lips. "We've come this far. We can't give up. Snape definitely has these ingredients!"
Harry's eyes widened. He understood what Hermione meant.
"Snape isn't like Professor Cavendish!"
"So, we just give up?" Hermione retorted.
Harry and Ron exchanged glances and finally gritted their teeth.
"Let's do it! The last class today is Potions. Let's prepare then!"
The three reached an agreement. As they came out of the bathroom, ready to go to class, they suddenly noticed a commotion in the hallway ahead.
Curious, they hurried over and discovered that another attack had occurred!
And the petrified victim was Colin Creevey!
Harry and his friends froze in place, their eyes filled with shock and disbelief.