Ma Xiao still suppressed his impulse, helped Li Mu remove the mines, and then continued to move forward. When it was just nightfall, he arrived at the edge of the city.

All cities have isolation walls, and Nanhu City is naturally no exception. Moreover, because the rebels did not have resistance, the isolation wall was well preserved. There will not be guards in every place, but it will not be easier to sneak into the city through the tall isolation wall than to cross the jungle.

"It will be more troublesome here." Ma Xiao looked at the team members: "The main function of the isolation wall is to resist dangerous species. It is not only solid and thick, but also has an alarm protection system. So we cannot climb over it, and we can only pass through the hidden door on the wall. The hidden door is designed to protect humans. We only need to activate the escape system of the isolation wall and we can go in..."

The isolation wall is the line of defense to protect the city, but it also has hidden dangers. Once something happens in the city, this wall will become the biggest obstacle. Although this possibility is not high, it must be considered when building. Therefore, any city isolation wall has many secret doors.

The secret door matter is confidential, and ordinary civilians and even ordinary officials will not know it. But for the students of the First Military Academy, these can only be considered common sense. So no one understands why Ma Xiao talks about this with a serious look on his face.

While Ma Xiao was doing popular science, Li Mu did not listen to it, but ran to the isolation wall and touched this and that curiously.

As an important defense facility in the city, it is strictly forbidden for idle people to approach each other on weekdays, and even visits are not allowed. Especially outside, almost no one can see it. This is the first time Li Mu has observed it from a close distance.

While groping, Li Mu exclaimed.

How come there are locks here?

The wall touched seemed smooth and flat, no different from other places. But Li Mu almost instantly determined that there was a lock here.

During the months in the mental hospital, in order to lock Li Mu up, the hospital changed almost all the locks that could be used. Thanks to that experience, as long as it was a lock on the Thunder Cloud Star, no matter whether it was a high-end or low-level one, there was basically nothing that Li Mu didn't know.

Li Mu knew that there was a secret door in the isolation wall, so he touched it and wanted to try to find it. But there would be no lock on the secret door, so it was obviously installed by someone later.

The isolation wall has security codes, and the modification permissions are in the Planet General Administration. No matter how long the rebels occupy Nanhu, they cannot change the security code unless the isolation wall is demolished and rebuilt.

Li Mu thought about it. The rebels occupied the Nanhai City for a long time. Although they could not get federal authority to change the security code of the isolation wall, it would not be too difficult to destroy it. For example, some secret passages were built on the basis of the secret door, entering and exiting or hiding from here, and sneaking into and attacking the federal army.

The federal army may not be unaware of the existence of these secret doors, and must have conducted large-scale investigations. However, there are too many, so there will inevitably be missed.

The place I found now is very hidden, using extremely sophisticated dark locks. But as a lock-opening master who has been studying in a mental hospital, how could he be so difficult to survive?

The source energy body of the dark lock is not nearby, so Li Mu cannot copy it. However, there are many ways to pick the lock, and it does not necessarily have to rely on the second barrier.

Li Mu took out a small tool kit, injected the source energy into the dark lock, and tinkered it on the wall.

While Li Mu was working on picking the lock, the students and Ma Xiao were still communicating about the secret door.

"Captain, the escape system is on the inside, and it is basically impossible to open the outside."

"It's hard to open, but there's still a way." Ma Xiao said: "I have security codes for all the isolation walls in the new third zone, which can be controlled from the outside."

The students looked shocked.

The security code of the isolation wall is the highest secret of the city, and usually only the mayor and the commander of the security district will know it. But their senior is actually capable of getting all the security codes of the three districts.

"But even if there is a security code, it doesn't mean that the escape system can be activated..." Guo Peng thought for a while: "If I remember correctly, the escape system activation requires a lot of authorization, and it is impossible to do it with just one security code."

"That's right." Ma Xiao said: "But the core principle of the escape system is to protect humans. As long as the system determines that humans are in danger, they can be activated without authorization. Moreover, we are not starting the entire system, we just open one of the secret doors."

"How to do it?" someone asked.

"Let the system determine that human life is threatened." Ma Xiao emphasized this sentence with aggravated words and looked around everyone: "The approach is a bit complicated, so I won't explain it in detail to you. To put it simply, I need a victim."

The students who were eager to try before were all stunned as if they were splashed with cold water on their heads.

"What? Didn't you realize the sacrifice before you came?" Ma Xiao smiled and said, "Ahem, have you been quite unconvinced all the way? Why is it that when there is a need, no one can stand up?"

"Senior, we are not afraid of death." Guo Peng's face turned red: "It's just that I didn't even see the shadow of the enemy, and I'm going to die for no reason. It's really a bit..."

"There are many kinds of sacrifices, and not everyone will die at the hands of the enemy." Ma Xiao sighed: "You are too naive, which is why you are unwilling to take you to carry out missions. If it were an experienced veteran, why should I explain so much? As long as there is one order, someone will do it..."

"I'll do it!"

"No, I'll do it!"

"And I..."

The military academy students felt insulted and stood up one by one.

Because it is too close to the city, no one shouts loudly. But the red face and the vigorous fists all confirm the excitement of the students.

As Guo Peng said, this method makes them unwilling to accept it, but no one is afraid of death.

Just when the students were passionate, Li Mu made a breakthrough.

With a click, something seemed to be opened in the wall, and a small piece slowly rose. Li Mu groped on the edge, grabbed a clamp ring, and with a little force, a secret door was pulled open by Li Mu.

Ma Xiao turned his back to the wall and did not see this scene, but the students watched it in real detail.

At first, everyone didn't care what the deputy captain was doing, but a dark door hole suddenly appeared on the wall, so how could they not notice it?

The students' voices and movements froze, and their voices became hoarse.

"What's wrong? Can your courage last for so long?" Ma Xiao smiled mockingly.

"Captain, where..." Guo Peng pointed.

Ma Xiao frowned and looked back. He happened to see Li Mu crawling into the wall, leaving only his big butt twisting outside.

"It seems like you can get inside..." Li Mu waved his hand outside: "Who has flashlight or something, use it for a while, it's too dark..."

Ma Xiao's eyes kept twitching, and the students' faces were even more exciting.

"Captain." Guo Peng looked at Ma Xiao: "Didn't you just say that you need to sacrifice one person to open the secret door?"

“We need an explanation.”

"Yes, Captain, you are talking..."

Facing Guo Peng and the students' questioning and even dissatisfied gazes, looking at Li Mu's butt, Ma Xiao didn't want to say anything.

There is only one sentence if you really want to say.
Chapter completed!