You went on a blind date and presented an A-level wanted criminal as a meeting gift?

The second test was held in a separate building in Area B of the base.

As Lin Chen followed the guide inside, a familiar scent filled the air.

Formalin, old blood, lime powder.

He reflexively thought of Jiang Tingxue.

Then I suppressed that thought.

This is not the time to think about women.

The examination room was a room of about 60 square meters, which was set up as the scene of a locked-room murder.

The room's furnishings belonged to a middle-aged man living alone: ​​an old sofa, bookshelves, a writing desk, and a bed. All the furniture was in a seemingly natural position, but there was a large patch of dried, blackened blood on the floor.

Bloodstains stretched from the desk to the doorway, with several splatter marks in between.

The back of the sofa, the windowsill, and even the chandelier shade on the ceiling were scattered with a large number of interfering clues—fingerprints, hair, pieces of paper, buttons, half a pencil, a piece of broken watch glass, and a few fibers whose origins were unknown.

There are at least two or three hundred pieces of physical evidence, densely packed together.

The examiner stood behind the observation window outside the room, holding a thermos cup, and spoke into the microphone.

"This level's challenge: Constructing a high-IQ crime scene."

"The scene in front of you is a perfect replica of a locked-room mystery from ten years ago in the capital city that remains unsolved to this day. The special task force at the time spent one year and four months without being able to solve the case."

"The rules are simple: whoever can accurately reconstruct the killer's modus operandi within one hour and provide a basic sketch of the killer's characteristics will advance."

"Any items on site may be used, but external equipment is not allowed."

"Timer begins."

Ten candidates entered the room at the same time.

Most people's first reaction is to squat down and look at the bloodstains on the ground.

One contestant with a criminal investigation background lay down on the floor, visually examining the angle of the blood splatters. Two technically skilled contestants began searching for clues on the bookshelves and writing desks.

Xiao Kuang stood at the door, frowning as he looked at the things.

He came from a demolition background, and criminal investigation wasn't his forte, but he picked up the preliminary forensic report on the table and began to study it diligently.

Lin Chen walked to the door and stopped.

He did not go into the room.

He stood right outside the threshold.

All three skills are activated simultaneously.

[God-level Trace Identification Technique] He unfolded all the physical and chemical residues in the room into a complete timeline map in his mind.

The angle of each drop of blood splatter, the degree of oxidation of residual grease in each fingerprint, and the origin and breakage method of each fiber are all automatically classified within a fraction of a second.

Of the more than two hundred clues, no more than ten were of value. The rest were all distractors.

[God-level psychological profiling] Based on the overall scene setup and murder method, construct a psychological model of the perpetrator in the mind.

The knife was placed slightly to the right of the neck at a downward angle, indicating that the assailant was approximately 175 centimeters tall, which was the perfect angle for the attack when facing the victim. The blade was angled three degrees to the left, and the force was applied from right to left.

left handed.

The most interesting detail at the scene was that the killer rearranged the items on the writing table before leaving.

The pen and book were arranged in perfect parallel lines, a sight only someone with obsessive-compulsive disorder would create.

A murderer who killed someone tidied up his desk before leaving.

Mild obsessive-compulsive tendencies, a cleanliness fetish, and likely to work in a profession requiring high precision.

But none of these are the most crucial.

Most importantly, it's a secret room.

The door was locked from the inside, and the windows were intact, showing no signs of external damage.

The victim died alone in a locked room, which appeared to be suicide, but the location and depth of the wounds on the forensic report ruled out suicide.

The task force got stuck here ten years ago.

They couldn't find out how the murderer left the locked room after the killing.

Lin Chen's gaze fell on the central air conditioning vent on the ceiling.

[Master of Architectural Science] told him that the central air conditioning duct in this room is connected to the main unit outside the building. The diameter of the duct is large enough for an adult's arm to fit inside, but not large enough for a person to crawl through.

It's not a passageway for people to walk on.

It is the path of the organization.

Lin Chen's gaze moved down from the air conditioner vent and stopped at the door lock.

The door lock is an old-fashioned spring-loaded bolt lock, which can be locked by rotating the handle from the inside.

Once the latch pops out, it locks into the keyhole in the door frame, thus locking the door from the inside.

He looked back at the ceiling.

The area directly below the air vent is not the door lock.

However, there was an inconspicuous water stain on the louver of the air vent.

It's very faint; ten years have passed and it's almost undetectable.

That wasn't an ordinary water stain.

Those are the dripping marks from the condensation when the air conditioner is running.

At this moment, Lin Chen's brain completed the final piece of the puzzle.

Air conditioner condensate.

Water-soluble silk thread.

Delayed deadbolt mechanism.

After committing the murder, the killer used a water-soluble thread to connect the door lock handle to the louvers of the air conditioner vent.

The thread passes through the gap in the blinds, with a tiny counterweight tied to the other end.

Then the murderer calmly opened the door, walked out of the room, and gently closed the door behind him.

The air conditioner runs continuously, and condensation drips onto the wires.

Water-soluble threads gradually soften, dissolve, and break when exposed to water. At the moment of breakage, the counterweight, under the influence of gravity, pulls the door lock handle to rotate, the bolt pops out, and the door is locked from the inside.

The thread then completely dissolved in the condensate and was flushed into the air conditioner drain pipe, leaving not a trace.

A delayed locking mechanism that can be activated without human presence.

The only trace left was an almost invisible water stain on the louvered air vent, a droplet of water splashed out when the threads dissolved.

The entire analysis took less than one minute.

Lin Chen turned and walked toward the examiner outside the observation window.

The other nine people in the room were still engrossed in searching for clues, and some had even knelt on the ground scratching at the bloodstains with their fingernails.

No one noticed that Lin Chen had already left.

The examiner frowned when he saw Lin Chen approaching.

"Give up?"

"I'm done answering."

The examiner was taken aback.

Lin Chen picked up the marker next to him and quickly wrote a few lines on the answer whiteboard.

Modus operandi: The perpetrator used dripping condensate from an indoor air conditioner, along with a water-soluble thread, to create a delayed deadbolt mechanism. After the perpetrator left the house normally, the thread dissolved and broke due to the condensation, and the weight of the thread caused the door handle to rotate, thus locking the door.

The perpetrator's profile: approximately 175cm tall, left-handed, with mild obsessive-compulsive disorder, and engaged in precision work.

It's finished.

Lin Chen put the pen cap back on and returned it to its original place.

The examiner dropped his thermos.

The lid popped off, spilling tea all over the floor. The thermos rolled twice on the stone floor before stopping, making a grating metallic scraping sound.

But the examiner completely ignored it.

He stared at the words on the whiteboard, his mouth agape.

His mind raced as he compared the internal report from the task force, which had been sealed in a top-secret archive ten years ago and had just been approved by the highest levels to be used as an exam question.

The modus operandi was exactly the same.

The killer's distinctive features were captured in a portrait, word for word.

They even accurately hit the core keyword "water-soluble silk thread".

It took the task force eight months to detect trace amounts of silk protein degradation products in the residue of the air conditioner drain pipe, which led to this conclusion.

This person stood at the door for less than a minute.

They didn't even go into the room.

The examiner looked up at Lin Chen as if he had seen a ghost.

The other candidates in the room gradually noticed something was amiss.

Someone came out, saw what was on the whiteboard, and stood there motionless for a long time.

Xiao Kuang was the last to come out.

He glanced at the answers on the whiteboard, then looked at Lin Chen, who was leaning against the wall with his eyes closed, resting.

His Adam's apple bobbed up and down, but he didn't say anything. He turned and left.

My steps were much heavier when I left than when I came.