The concrete ceiling above had already shown several cracks.

It looks like it's about to collapse.

Qin Fei and Xie Nanai immediately fled into the laboratory behind them. At the same time, he threw a match outside the laboratory.

As soon as the match fell, the entire ground was instantly lit with gasoline.

As the crack continues to expand, the ceiling at the top is finally dug out by the zombies with a large hole.

Countless zombies have fallen from here.

It's very disgusting, and it looks like there's a lot of it.

Qin Fei glanced at it.

Even if you don't count the zombies that haven't fallen yet, it's estimated that there will be about thirty or forty of these zombies that have fallen to the ground.

And above the entrance of the cave, the low roars and footsteps of zombies were still heard. It is estimated that there are still some zombies that have not yet fallen from the entrance of the cave.

It took almost two hours for the zombies to dig up to this location from the ground. After this period of accumulation, it is not surprising that so many can appear at one time.

Ordinary zombies and zombie dogs were quickly burned to death in this fire.

Because the military fat and fat zombies were too fat and had a lot of body oil, they also failed to hold out in the fire for a long time, and they blew themselves up.

When zombies attack human camps, they will actively avoid obstacles, traps, and flames.

Unless you set the whole camp on fire and leave no way. Otherwise, the zombies will find a place that is not set on fire to attack.

It's simple to light a fire somewhere. But if you want to set fire to the entire area of the camp, no camp can afford to use the fuel.

What's more, the tide of corpses will last for a full eight hours at night.... This means that you have to prepare enough fuel to burn for eight hours....

Therefore, in general, with the exception of Molotov cocktails that can be thrown, survivors will rarely use fire attacks to defend against the zombie tide.

That is, Qin Fei just found some gasoline in this research institute, plus he only needed to hold on for one more night to return, so there was no need to keep these gasoline.

That's why he was able to use fire attack so extravagantly.

Soon, before the gasoline on the ground burned out, the fire was gradually starting to get smaller.

After all, this is underground, and the amount of oxygen in the air is limited.

Although the institute was built by the military and had good ventilation, the oxygen in the air could not withstand the constant burning of the fire.

The fire slowly stopped.

From the pile of burned zombies, nearly a dozen zombies covered in green light crawled out.

These green-skinned zombies weren't burned to death by the fire.

The green-skinned zombie has a strong physique and is extremely resilient. In addition, the fire did not burn for long, so they recovered quickly.

The lack of oxygen in the environment has no effect on these green-skinned zombies.

The zombies in the Seven Days Killing World can still survive even underwater, and the actions of these zombies do not need to consume oxygen at all.

The recovered green-skinned zombies rushed to the laboratory one after another, and began to attack the walls and doors of the laboratory.

However, these walls are made of industrial cement, mixed with sand and gravel, and poured on steel bars.

Its quality is far from being comparable to the inferior products that Qin Fei burned out of an earthen stove.

So even these green-skinned zombies have to spend a lot of effort to cut them open.

Xie Nanai looked at the green-skinned zombies outside the laboratory, stuck out his tongue, and breathed a long sigh of relief.

"It's okay, it's okay, it's just such a zombie, it should be able to keep it."

"Indeed."

Qin Fei also agreed at this moment.

Count the Super Corn Breeding Room, the Green Pig Room, the Soldier's Lounge, the Pure Steel Square Room, and the Lab on the Bottom.

The underground institute has five floors of rooms from top to bottom.

And almost every floor of the space is built with steel gates and concrete walls.

According to the destructive power of these ten green-skinned zombies, even if they dig until six o'clock in the morning, they will not be able to dig the bottom layer.

Thinking of this, Qin Fei's mood also relaxed at the moment.

At the same time, Xie Nanai, who was standing beside Qin Fei, suddenly raised his head, looked at the top of his head and said, "I have a hunch, it is estimated that there are still above!" ”

She had just finished saying that.

Immediately, two zombies with gray-red skin fell from the hole outside the research institute.

The two zombies were slender and had their teeth turned out. The blood vessels and green tendons all over the body bulged out, and it looked extremely hideous.

The most important thing is that most of the internal organs in their bodies are exposed from the location of their abdomen.

The appearance of this zombie is too familiar to Qin Fei.

Isn't this the corpse king in the Seven Days of Killing!

Depend on!

As soon as Xie Nanai finished speaking, two corpse kings came.

Seeing this, Qin Fei glanced at Xie Nanai beside him with a surprised face.... How can this guy's premonition of danger be so accurate?

The Corpse King is very difficult to deal with.

In the previous versions of the game, the Corpse King has always been the most powerful existence among zombies.

As a mutant who only appeared in the last wave of corpses... Qin Fei didn't need to try to know that even if he and Xie Nanai had trolls as weapons, they were definitely not the opponents of this corpse king.

The point is that there are two more of them.

After these two corpse kings also joined the demolition team, cracks soon appeared on the walls of the laboratory.

Qin Fei's original plan was to use the fifth-floor room of the research institute to use a shotgun to fight and retreat, slowly delaying time.

But just these ten green-skinned zombies are no longer something that the two of them can deal with head-on.

Not to mention, there are also two corpse kings by their side.

The tactics of fighting and retreating and delaying time have no meaning at all in front of these zombie mutants.

Because the danger level is too high.

Therefore, Qin Fei and Xie Nanai retreated directly to the bottom of the research institute, waiting for the arrival of these mutant zombies.

2 o'clock in the morning.

[Countdown to the return of the mission: 4 hours 0 minutes]

The speed at which the Corpse King ploughed the ground was really unbelievable.

After these two corpse kings joined, in just two hours, these zombies had already dug out the bottom of the laboratory.

The concrete walls of this laboratory are the same thickness as the outside.

According to the calculation that these zombies dug through four rooms in two hours, the laboratory where Qin Fei and Xie Nanai were located could only last for half an hour at most.

I can't beat it, I can't drag it out.... It's almost a game of death.

"What now?"

Looking at the zombies outside frantically gouging the walls, Xie Nanai was about to cry in the laboratory.

She restlessly walked around the lab.

Qin Fei frowned and didn't say a word.

"Hey! There are ladders in the toilet to climb! "Xie Nanai, who kept walking around the laboratory, found a passage that seemed to lead to the ground.

It is a vertical passage only one person wide, with a long ladder for people to climb to the ground.

"I already knew, useless." Qin Fei shook his head and said, "We couldn't outrun the green skin, the corpse king ran faster than the green skin, and when he got to the ground, it was equivalent to sending him to death..."

It's not surprising that there are secret passages in the institute.

In the Seven Days Kill game, almost all buildings with complex structures have a secret passage.

This is also set up so that the player can go out quickly after looting the building without having to go back the same way.

Qin Fei felt a little desperate in his heart.

Is there no other way?

It shouldn't be!

If the survival chance given by the system is zero, then it is better to kill Qin Fei and the others directly... Fei sent them to this world so vigorously, it must not be for them to die.

The system is unlikely to come up with a completely unsolvable situation.

There will definitely be a way to break the game.