Library Clues

The first week of November.

Hogwarts's temperature had dropped sharply by ten degrees. A thin layer of frost covered the grass by the Black Lake, and morning physical training had become something that required courage.

The white vapor Ron Weasley exhaled while running looked like a miniature steam engine.

"I think—my lungs—are freezing—" he panted as he ran.

"Your lungs won't freeze." Artoria jogged steadily at the front of the group, her breathing not even quickening. "The human respiratory tract has sufficient warming capacity. The cold you feel is merely an illusion caused by the drop in surface temperature."

"This illusion—is about to kill me—"

"Keep running. Four hundred meters left."

Ron let out a sound somewhere between a wail and a roar and kept forcing his legs forward.

Zhang Wen ran in the middle of the group. After two months of training, his mile-and-a-half time had finally broken twelve minutes. He was still in a completely different dimension from Artoria, but at least he was no longer near the bottom of the class.

This "class" included twelve-year-old students.

Zhang Wen chose not to think about that.

Tuesday afternoon, there were no classes.

Zhang Wen was in the library, looking through texts on Dark Magical Creatures that lived in water.

Hogwarts's library held an astonishing number of books. The "Magical Creatures" section alone took up two shelves, while the dedicated "Dark Magical Creatures" section was crammed with hefty old volumes from every era.

Zhang Wen had been searching for three days already.

He was looking for one particular keyword: "corrosive aquatic creatures."

Most of the texts pointed toward known species: Grindylows, Kelpies, Water Sprites, Sirens. Each had its own dangers, but none caused nearby plants to wither and the soil to deteriorate.

Until he found an old book with a blackened cover—Dark Records of British Waters, written by a wizard named Hector Dagworth and published in 1743.

The title of the book's seventh chapter was: "On Cursed Waters and the Creatures Dwelling Within."

Zhang Wen turned to that chapter and began reading line by line.

"...In the northern Scottish Highlands, lakes occasionally undergo mutations due to Dark Magic contamination. The waters of such lakes take on an inky black hue, and any organic matter that comes into contact with them rapidly decays and rots. If the source of contamination is an artificially placed Dark Magic medium—such as a cursed stone, bone, or blood—the native organisms in the lake may mutate: growing larger, changing their habits, and gaining corrosive magical power..."

Zhang Wen's finger stopped over the words "cursed stone."

A black stone.

The black stone Angus's neighbor had picked up by the lake.

"...Such mutated creatures are commonly called 'Dubh-Loch Beasts.' Their characteristics include: a size of four to eight meters, no fixed form, feeding on living creatures, and an aversion to sunlight and fire. Their bodily fluids are highly corrosive, capable of killing plants, rusting metal, and weathering stone."

Zhang Wen read on quickly.

"...The creation of a Dubh-Loch Beast requires three conditions: first, a freshwater lake as a vessel; second, a Dark Magic medium as a catalyst; third, native life in the lake to serve as the basis for mutation. In other words—a Dubh-Loch Beast does not appear out of thin air. It is gradually mutated from an organism originally living in the lake, under the continued influence of a Dark Magic medium."

Zhang Wen put down the book and leaned back in his chair.

Glenmore Lake had once been "quiet as death"—the old villagers' words. But there had certainly been fish or other aquatic creatures in the lake. The black-cloaked figure had placed a cursed stone there. The stone released Dark Magic energy, and some creature in the lake absorbed it and began to mutate.

In two months, an ordinary fish had become a four- or five-meter-long Dubh-Loch Beast.

"As for methods of destroying a Dubh-Loch Beast—" Zhang Wen turned the page.

The page was blank.

No, it was not blank. It had been torn out.

The next page—the chapter on how to destroy it—had been neatly ripped from the binding.

Zhang Wen stared at the torn edge. The cut was fresh. This book had sat in the library for more than two hundred years, but the tear looked only a few weeks old.

Someone had torn out that page recently.

Zhang Wen closed the book and glanced at the borrowing record on the inside cover. Every book in the Hogwarts library had an automatically recorded borrowing stamp—who had borrowed it, and when.

The most recent borrowing record was dated October 3. The borrower's signature had been covered by a blot of ink—deliberately obscured.

October 3. About five weeks ago.

Zhang Wen closed the book and took it to Madam Pince's desk.

"Madam Pince, this book was damaged recently. Part of Chapter Seven was torn out."

Irma Pince—the Hogwarts librarian—looked at the book with a gaze that could kill. She snatched it away and flipped it open. When she saw the torn pages, her face turned darker than Snape's.

"Who did this?!" Her voice was sharp enough to cut glass.

"The borrowing record was erased."

Madam Pince's trembling fingers flipped to the borrowing record page. When she saw the blot of ink, her lips pressed into a thin line.

"My books." Her voice dropped low, somehow more terrifying than shouting. "Someone destroyed my books."

Zhang Wen felt that if Madam Pince found the person who had torn out those pages, their fate would probably be worse than being stared at by a Basilisk.

"Madam Pince, the contents of this book are important to an investigation I'm conducting. The torn pages recorded how to destroy a creature called a Dubh-Loch Beast. Do you have any other way to find that information?"

Madam Pince thought for a while.

"There was only one edition of Dagworth's book. It was never reprinted," she said. "But some of his manuscripts are kept in the Restricted Section."

The Restricted Section.

Zhang Wen had professor-level authorization and could enter the Restricted Section.

"Thank you. I'll go look."

"Tell me if you find the person who damaged that book," Madam Pince said viciously. "I'll make him understand the consequences of damaging books in my library."

Zhang Wen felt that this woman should become the Defense Against the Dark Arts professor. Her intimidation was more than sufficient.

The Restricted Section lay at the deepest end of the library, separated by an iron gate.

Zhang Wen used a professor's access charm to open the gate. The air inside was several degrees colder than outside, thick with the smell of mildew and old parchment.

The books on the shelves were older and more worn than those in the ordinary section. Some covers trembled faintly, while others gave off low groans. As Zhang Wen passed, a black leather book locked with chains suddenly opened, revealing a mouth full of sharp teeth inside.

"Hiss—"

Zhang Wen took a step back.

"Quiet," he said.

The book shut itself, letting out a dissatisfied grumble.

It took him about twenty minutes to find Dagworth's manuscripts—a stack of yellowed parchment tied together with string and placed in a dust-covered box.

The handwriting in the manuscripts was extremely messy. Eighteenth-century wizards wrote very differently from modern people—their letters were strangely shaped, abbreviations were everywhere, and there were occasional passages in Latin and Old Gaelic.

It took Zhang Wen half an hour to find the section describing how to destroy a Dubh-Loch Beast.

He translated it word by word.

"...The destruction of a Dubh-Loch Beast must begin at its source. Its vitality comes from the Dark Magic medium—the cursed object cast into the lake. If that medium can be found and destroyed, the Dubh-Loch Beast's supply of magical power will be cut off. Once deprived of magical power, the Dubh-Loch Beast will regress to its original form within several days..."

Destroy the medium.

The problem was that the medium was at the bottom of the lake.

Zhang Wen kept reading.

"...However, retrieving the medium is by no means easy. A Dubh-Loch Beast will instinctively protect the source of its magical power. Any creature approaching the medium will be attacked. Therefore, the standard procedure for destroying a Dubh-Loch Beast is as follows: first, lure the Dubh-Loch Beast away from the medium's location; second, dive to the lakebed during its absence to retrieve or destroy the medium; third, wait for the Dubh-Loch Beast to regress due to the loss of magical power."

"If the Dubh-Loch Beast cannot be lured away, it must be confronted directly. Dubh-Loch Beasts fear fire and light. Iron can harden their outer surfaces and slow their movement. Piercing its inner core with an iron spear or iron sword—usually located slightly below the center of its body—can inflict a fatal wound. But take care—the bodily fluids of a Dubh-Loch Beast are highly corrosive. Anyone engaging it in close combat must wear full-body protection, otherwise—"

The manuscript ended abruptly there. The remaining portion had been eaten away by insects, leaving only a few blurry fragments of letters.

Zhang Wen copied down everything he could read.

The key information was enough:

First, the Dubh-Loch Beast's vitality came from the Dark Magic medium at the lakebed—the cursed stone.

Second, destroying the medium could make the Dubh-Loch Beast regress.

Third, if direct combat was necessary—it feared fire and light, iron was effective, and its core was slightly below the center of its body.

Fourth, its bodily fluids were highly corrosive, and close combat carried the risk of corrosion.

Zhang Wen put away his notes and left the Restricted Section.

He paused at the iron gate.

Someone had borrowed this book on October 3, torn out the pages describing how to destroy the creature, then erased the borrowing record.

That person did not want anyone to know how to destroy a Dubh-Loch Beast.

Combined with what had happened at Glenmore Lake—a black-cloaked figure had performed a ritual beside the lake at the end of August—

The person who tore out the pages and the black-cloaked figure might be the same person.

This person could enter the Hogwarts library.

Zhang Wen returned to his office with his notes.

Artoria was not there—she was giving Neville Longbottom individual training that afternoon.

Zhang Wen sat at his desk and organized all the information into a complete file.

Glenmore Lake incident timeline:

Late August—the black-cloaked figure performed a ritual by the lake and placed the cursed stone.

Early September—the creatures in the lake began mutating. The first sheep disappeared.

October 3—someone borrowed a book about Dubh-Loch Beasts from the Hogwarts library, tore out the pages describing how to destroy them, and erased the borrowing record.

Mid-October—Angus discovered the anomaly and asked McGonagall for help.

From late October until now—the Dubh-Loch Beast's range of activity had continued expanding. A magical power spike appeared every afternoon between three and four, suggesting that it was receiving external instructions.

Zhang Wen stared at the date "October 3" for a long time.

October 3.

By then, Zhang Wen had already been at Hogwarts. The Chamber of Secrets Incident had not yet been made public. Everything at the school had been normal.

The people who could enter the Hogwarts library on October 3—

Students, staff, or outside visitors with legitimate reasons to visit the school.

If it was a student—what student would know about an obscure Dark Magical Creature like a Dubh-Loch Beast?

If it was a staff member—

Zhang Wen shook his head. He did not want to think in that direction. But logically, it could not be ruled out.

If it was an outside visitor—had anyone visited Hogwarts in early October?

He needed to check the school's visitor records.

At dinnertime.

Zhang Wen found an opportunity to sit with Professor McGonagall in the Great Hall.

"Professor McGonagall, did any outside visitors come to the school in early October?"

McGonagall thought for a moment.

"A group of parents came for Parent-School Liaison Day on October 2. On October 4, two people from the Ministry of Magic came for a routine inspection."

"Which parents attended Parent-School Liaison Day?"

"The list is in the files in my office. Do you need me to check it?"

"I'd appreciate it."

"Is this related to Glenmore Lake?"

"Possibly."

McGonagall nodded without asking further questions.

Zhang Wen turned to Artoria. She had just returned from the training grounds and was demolishing a plate of roasted chicken legs at an astonishing speed.

"I found information about that thing in the library," Zhang Wen said in a low voice. "It's called a Dubh-Loch Beast. It's an aquatic creature mutated by a Dark Magic medium. The way to destroy it is to destroy the medium at the bottom of the lake—that cursed stone."

Artoria's chewing slowed by a beat. In her behavioral patterns, that was equivalent to "highly attentive."

"There's something else," Zhang Wen said. "The pages describing how to destroy it were torn from the book. October 3. The borrowing record was deliberately erased."

Artoria put down her knife and fork.

The seriousness of that gesture was roughly equivalent to an ordinary person flipping the table.

"Someone is operating inside Hogwarts," she said.

"Yes. This person knows the Dubh-Loch Beast exists, knows how to destroy it, and deliberately destroyed that information."

"To stop others from destroying the Dubh-Loch Beast."

"To protect something he created."

The two looked at each other for a second.

"The nature of this matter has changed," Artoria said. "It has gone from 'destroying a Dark Magical Creature' to 'fighting an enemy hidden in the shadows.'"

"And that enemy is connected to Hogwarts. He can enter the library, knows what is in the Restricted Section, and understands obscure Dark Magic creature lore."

"A staff member or an older student."

"Or an outside visitor with authorization to enter the school. A parent, Ministry official, or board member."

Artoria picked up her knife and fork again.

"We need to narrow it down."

"McGonagall is checking the visitor list from early October. I'm also planning to ask Snape for help—he knows the intelligence network of Slytherin students and pure-blood families best. If the person behind this is connected to the pure-blood circles, Snape may have a clue."

"You trust Snape that much now?"

"After the Chamber of Secrets Incident, he said, 'Don't leave me out of this.' I chose to believe him."

Artoria considered it, then nodded.

Then she cut off a piece of chicken and put it into her mouth.

Information processed. Back to normal mode.

After dinner, Zhang Wen ran into Hermione in the corridor.

She was carrying—as usual—a stack of books. But today's books were different from her usual ones. Zhang Wen glanced at the titles on the spines: Mysterious Legends of the Scottish Highlands, Illustrated Guide to Magical Creatures of the Waters, Dark Magic Contamination and Environmental Mutation.

"Miss Granger," Zhang Wen called to her. "What are you researching?"

Hermione's face reddened slightly.

"I heard Harry talk about Glenmore Lake," she said. "After he came back, he told Ron and me about the investigation—of course, he said you told him to keep it secret—but he thought I might be able to help—so he only told us the general idea—"

"He told you all the details, didn't he?"

Hermione's face turned even redder.

"...More or less."

Zhang Wen sighed. Asking Harry to keep a secret was about as realistic as asking Fred and George not to pull pranks—possible in theory, impossible in practice.

"What did you find?"

Hermione's eyes immediately lit up. She stacked the books on the corridor windowsill and opened one of them.

"I looked into records of unusual incidents in lakes across the Scottish Highlands. Glenmore Lake had a similar event in its history—in 1634, nearby villagers reported a 'black demon' appearing in the lake. It took a wizard hunter three months to destroy it."

"1634?" Zhang Wen took the book and glanced through it. "How did that wizard hunter destroy it?"

"The records aren't very detailed. They only mention that he 'bound the demon to the shore with iron chains and burned it with holy fire.'"

Iron chains. Fire.

It matched the information in the Dagworth Manuscript.

"There's another point." Hermione turned to another page. "Before the 1634 incident, people had also seen 'strangers in black robes' by the lake."

A chill ran down Zhang Wen's spine.

1634 and now—nearly four hundred years apart—yet the pattern was exactly the same. Black-robed figures appeared, creatures in the lake mutated, and the Dubh-Loch Beast was created.

"What do you think that means?" Zhang Wen asked Hermione.

Hermione bit her lip. She was choosing her words carefully.

"I think—it might be the same ritual," she said. "Someone has mastered a method of creating Dubh-Loch Beasts, and that method has existed for at least four hundred years."

"Or longer," Zhang Wen added.

Hermione's expression turned serious.

"Professor Zhang, can I help investigate more documents? There must be other relevant records in Hogwarts' library. I read very quickly, and—"

"Alright," Zhang Wen said.

Hermione froze. She had probably been prepared to be refused, and had even prepared a whole set of arguments to persuade him.

"Really?"

"Your research ability is the strongest I've seen in any twelve-year-old student. I need someone to systematically sort through the literature. You're better suited to this job than anyone else."

Hermione's face lit up.

"But there are conditions." Zhang Wen raised one finger. "You are not to access anything in the Restricted Section on your own. Report to me first if you find any relevant leads. And—do not let it affect your regular studies."

"I promise it won't!"

"And—don't go to Glenmore Lake. It's dangerous there."

"I know. I'll only do document research."

Hermione gathered up her books and left. Her steps were much lighter than when she had arrived.

Watching her retreating back, Zhang Wen suddenly felt that he had assembled a rather good team.

Artoria was responsible for combat and training.

Snape was responsible for intelligence and investigations in the Slytherin direction.

McGonagall was responsible for administrative support and outside contacts.

Filius Flitwick provided technical equipment.

Hagrid provided logistical support—roosters.

Hermione was responsible for document research.

Harry was responsible for field investigations and tactical coordination.

Malfoy—

Malfoy's role was still unclear. But his performance in the Scottish Highlands showed that he had the potential to take on more. He needed further observation.

As for Neville Longbottom—

Neville Longbottom was growing. Going by Artoria's training progress, his combat ability might undergo a qualitative leap by mid-December.

Zhang Wen returned to his office and sat down.

A cup of tea sat on the desk. Steam still rose from it.

Artoria had already gone on patrol. But before leaving, she had made the tea.

Black tea. The temperature was just right. It was a little stronger than the tea he made himself.

It was like this every day.

Zhang Wen picked up the cup and took a sip.

Then he opened his notebook and began making a detailed plan for next Saturday's tracking operation at Glenmore Lake.

The clock on the wall showed 9:15.

Artoria was due back from patrol at midnight—his rule.

He had nearly three hours.

Enough.

His pen scratched across the parchment. Outside the window, the wind howled past the castle. Hogwarts was cold in November, but the office was warm.

The fire burned in the fireplace. The tea on the desk steamed.

The door to the room next door stood slightly ajar—that was Artoria's room. Her bed was perfectly neat, its blanket folded into a military square. Beside the pillow lay the thick volume of Hogwarts history she was halfway through reading.

After writing for a while, Zhang Wen looked up at the half-open door.

He realized he was counting the time.

Two hours and forty-five minutes until she returned.

Zhang Wen lowered his head and continued writing.

The sound of his pen filled the quiet room.