After tearing out all the pages and eliminating the "distracting options," Lin Yu and Furbollo quickly pieced together all the "puzzle pieces." The entire wooden floor was covered with the torn-out pages. This task was extremely time-consuming and laborious, and it was now well past midnight.

The scattered pages formed four large numbers on the floor: "9," "4," "5," and "7." Seeing these four numbers, Lin Yu nodded with satisfaction. "Good, the password should be some combination of these four digits. We just don't know the correct order yet..."

With four digits, there were 4! (24) possible permutations. Trying all 24 combinations one by one would be time-consuming but feasible. However, Lin Yu hesitated to gamble—what if the box had some self-protection mechanism that would destroy its contents after too many wrong attempts?

As Lin Yu squatted pondering this, Furbollo suddenly spoke up. "The correct sequence should be either 5497 or 7945... with 5497 being more likely."

Lin Yu looked at him in surprise. "How did you deduce that?"

Furbollo shrugged. "Simple. These books weren't randomly paired. Their contents are strongly related—they seem like textbooks from the same academic course. Adjacent books usually share similar difficulty levels, which increase in the order of 5497. The publication dates follow the same sequence."

Lin Yu was astonished. "You can tell that despite the blacked-out pages?"

"Of course," Furbollo replied calmly. "The amount of blacked-out area reflects the quantity and complexity of the formulas. Plus, there are obvious hints in the content." He squatted down and pointed at one page forming the "4." "See this footnote? It references content from book 5. Section 7 is also an extension of 5—but since 9 mentions both 4 and 7, with an 'Additionally' before describing 7, I suspect 7 supplements 4."

Lin Yu stared at him, impressed. Despite his eccentric demeanor, Furbollo's detective skills were undeniable. Lin Yu was starting to believe he really was a professional detective. "You remember all these minute details?"

"Piece of cake," Furbollo boasted. "I can even tell what these books are about from fragments. They discuss using 'emotions' as fuel and raw materials—"

*Click!* The sound of the lock opening interrupted Furbollo.

"Hey!" Furbollo glared at Lin Yu indignantly. "Can't you let me finish?"

While Furbollo had been monologuing, Lin Yu had already gone to try the combination. "Sorry," Lin Yu said without looking up as he opened the box. "I'm more interested in what's inside than the books' contents. We can discuss the dungeon's backstory later."

Furbollo sighed and joined him. "Fine, I'm curious too."

Inside the box was a transparent file containing three items: a black notebook, a white ID card, and a key—someone's personal belongings.

Lin Yu unceremoniously opened the file and examined the ID card. Its back bore a black logo of a burning book, while the front displayed basic information:

[Name: Vale Valetti]

[Gender: Male]

[Position: Independent Researcher]

[Clearance: B-3]

[Region: Extreme Winter Mountain]

A photo showed a gloomy young man with curly hair wearing a white dress shirt, his face partially scratched out.

"So this is the cabin's owner," Lin Yu muttered.

He then opened the notebook. Only the first third contained writing—research diary entries:

"August 7, Blizzard. Sensors detected a 'leak' here. Damn it, there's not a living soul around! How could there be a leak?"

"August 10, Blizzard. Slept poorly... Scouted the area today—nothing. Nearby settlements have been abandoned for years."

"August 15, Blizzard. Having constant nightmares—this place is awful. Why bother noting the weather? It's always snowing! Still no leads. One more week and I can leave."

"August 16, Blizzard. Dug up something disturbing... So many deaths here? And not a trace of residual souls on the bodies—highly abnormal!"

"August 17, Blizzard. There's a monster called 'Chate' in these mountains? My dreams grow more chaotic! Calling for backup once comms are restored!"

"August 25. What the hell is happening here? Why such terrifying creatures? My condition's deteriorating. Taking risks tomorrow!"

"August 26. Now I understand... No wonder it's called a 'leak.' Never imagined it would manifest this way. Our own mistakes caused this! So horrific!"

"August 27. I've figured out how to deal with 'Chate'!"

The diary ended abruptly, the remaining pages blank. The deteriorating handwriting mirrored the writer's worsening mental state. Lin Yu rubbed his temples. "Complicated indeed."

He exhaled deeply. The dungeon's "truth" was coming into focus—but it only gave Lin Yu more headaches. His goal wasn't solving the dungeon's mystery but finding the 'Fraudster.' Who had set up this 'scam' at Extreme Winter Mountain? He still had no leads.

Beside him, Furbollo suddenly spoke earnestly: "Thank you, May! Thank you for bringing me here!"

Lin Yu turned, puzzled by the detective's sincerity. "Why are you thanking me?" Hadn't he forced the 'detective' here at gunpoint?

Furbollo's eyes shone with fervor. "I initially thought this was just another survival dungeon, so I assumed any 'hidden puzzles' wouldn't be worth solving. I was wrong—this mystery is fascinating! Had you not discovered this place and forced me to come, I might have missed such an excellent puzzle!"

His face lit up with fanatical excitement. "Now, whether it's 'Chate' or this mysterious researcher... I'll uncover everything! The truth behind Extreme Winter Mountain!"