The neighborhood where the crime occurred.

Chen Yan, Qin Chuan, Huang Guojun, and the entire task force are basically here.

The outermost layer of the smoke exhaust hole is a protective cover that prevents cold wind from flowing back and is waterproof.

After the protective cover is removed, it is a one-way locking iron piece.

"Everyone, look here," Chen Yan pointed to the one-way locking iron piece: "Everyone knows the function of the locking iron piece."

Chen Yan used his fingers to lift the iron piece slightly: "Look, there is a faint half-moon-shaped scratch mark on the surface of the iron piece."

Qin Chuan stepped forward to check it out in person.

The scratches are very light and almost invisible.

If Chen Yan hadn't reminded him, Qin Chuan wouldn't have been able to tell if he looked carefully.

Huang Guojun also stepped forward to take a look and asked doubtfully: "Group Chen, this scratch...was it left by the murderer?"

"But how did he let the water heater exhaust gas flow back?"

Huang Guojun completely blocked the iron piece: "If the iron piece is completely blocked and oxygen-containing air cannot enter, the water heater will automatically turn off."

Chen Yan nodded: "This is indeed true, but what if the murderer can still make the iron piece open and close in one direction?"

"You see, under normal circumstances, this iron piece can be pushed open by the exhaust gas discharged from the water heater."

"But if you increase the weight of the iron piece, like this..."

Chen Yan took out a small semicircular black block and showed it to everyone.

"magnet?"

Liyang was surprised.

"Yes, it's a magnet!"

After Chen Yan attached the magnet to the iron piece: "Liyang, go to the room, turn on the hot water faucet, and let the water heater work."

"At the same time, close the doors and windows and use an instrument to detect the indoor carbon monoxide concentration."

…

After a while.

The water heater starts.

The iron piece that should normally open smoothly has increased in weight due to the adhesion of magnets, and now it cannot be pushed open by the exhaust gas from the water heater.

When Chen Yan took off the magnet, the iron piece lost weight and was suddenly pushed away by the exhaust gas.

Chen Yan knocked the magnet against the wall, took off half of it, and attached the iron piece again.

At this time, although the iron piece can still be pushed open by the exhaust gas again, the amount of pushing is obviously much smaller.

It's only about one-fifth of the original level.

A quarter of an hour later.

Liyang ran out of the room and looked at Chen Yan with surprise: "Team Chen, the carbon monoxide concentration in the room has increased!"

The root cause of carbon monoxide poisoning was found!

The murderer used a very simple device to achieve his intended purpose.

A small magnet.

The opening and closing degree of the one-way iron piece becomes smaller, which can not only block the exhaust gas and discharge it into the room, but also ensure that a certain amount of oxygenated air enters the water heater.

Keep the water heater running.

wonderful!

If there weren't some scratches on the one-way locking iron piece left by magnets, Chen Yan would never have thought of it.

Don't underestimate this.

The direct cause of death of the deceased was carbon monoxide poisoning.

But how on earth were the four deceased poisoned?

Regardless of whether the murderer can be caught or the case can be solved, this is a mystery that must be solved.

Even if the murderer is caught, the detective will not be able to figure out what the murderer did unless the other party tells him, and you will not be able to convict him.

Why?

The direct cause of death should be carbon monoxide poisoning.

To put it simply, the murderer later broadcast live in a WeChat group.

It was about dressing up the corpses, setting up the shapes, arranging the last supper, and finally turning the four corpses into dolls.

In fact, they are all an insult to the corpse.

Judging from the time of the video and the time of death of the deceased.

People who play with corpses and start live broadcasts with dolls are not necessarily murderers.

Because the cause of death of the deceased was carbon monoxide poisoning.

Poisoning is the root cause.

The rest are just clues for detectives to find the murderer.

And now, the most important link in the evidence chain has been cracked.

Return to the Hulu City Detective Team.

It’s 6pm on the 12th.

Qi Yuansheng brought further clues.

All 32 group members who watched the video have been contacted.

Among them, one of them happened to be in Hulu City.

Interrogation room.

"I really didn't know it was a body..."

In the monitoring room, Qi Yuansheng was introducing Chen Yan and Qin Chuan.

"This person's name is Yang Qi, he is 24 years old and he is a delivery boy from Hungry or Not Hungry."

"I have loved doll figurines since I was a child. Two years ago, while watching a live broadcast at night, I saw a video of Zhao Mingwei playing with dolls. I am a fan of Zhao Mingwei."

"Two years ago, I joined the WeChat group organized by Zhao Mingwei."

Ask indoors.

"We are just looking for you to understand the situation. As for the person doing the live broadcast, have you ever seen him in person before?"

"Really not," Chen Qi cried, his body trembling slightly: "We are just a group with common interests."

"Everyone usually shares their dolls in the group."

"We have never met each other. During the live broadcast, we always wore masks and did not show our faces."

"Ask him why he doesn't show his face during the live broadcast?"

In the monitoring room, Chen Yan gave instructions to the detectives in the interrogation room through the wireless microphone.

There are very few people who don’t show their faces during live broadcasts.

Why live broadcast?

Don’t you just want to be famous?

If you don’t show your face, why are you broadcasting live?

Of course, the characters created by some podcasters are private, but Zhao Mingwei is just a doll player, so that's not the case.

"Why don't you show your face during the live broadcast?"

As a result, as soon as the detective finished asking, Chen Qi's eyes were a little dodgey and his words were hesitant.

"This this……"

The interrogating detective was also a veteran, so he naturally saw something was wrong with Chen Qi.

"Chen Qi, I think you need to understand something."

"The live broadcast you watched on August 9th was not an ordinary doll dressing up, but a major live broadcast of murder with a particularly bad impact!"

"As a witness, you didn't discover or stop it, and you were even willing to watch!"

"Chen Qi, up to now, you are still hiding it?"

"No, no!" Chen Qi was obviously frightened.

"I'm not hiding it, but... I'm just too embarrassed to say..."

Half an hour later.
To be continued...