Yu Baiying also came over and carefully observed the hole, and found that it was about one meter in size, and there was a row of stone steps at the entrance.

Some messy footprints were also found on the edge of the cave, which was obviously visited by people from time to time.

So Yu Baiying turned around and looked at the soles of the slain ninjas, which happened to match the footprints in the cave.

"This cave should be the secret passage for those ninjas."

Yu Baiying came to this conclusion, and then said to Su Yuan: "If you go down rashly, I'm worried that there is an ambush inside!"

When Su Yuan heard this, he immediately used his mind to investigate the cave...

Although Su Yuan's "clairvoyance" has been inexplicably interfered with and cannot be used temporarily, his spiritual sense is still powerful and can detect situations and even crises within a certain range.

"There is no ambush in this cave for the time being. Let's go down and take a look right away! We might have a chance to find the lair of those ninjas, and we also need to find the whereabouts of Xiao Ling and rescue her!"

Su Yuan said this to Yu Baiying.

"good!"

Yu Baiying immediately agreed. Because Lan Qingling was taken away, she felt quite guilty and wanted to find her whereabouts and rescue her as soon as possible.

Afterwards, Su Yuan and Yu Baiying walked down the stone steps of the cave.

The stone steps were not too deep, about ten meters or so. After the two of them walked to the bottom of the stone steps, they discovered that there was a rather spacious tunnel.

Moreover, there are wall lamps on both sides of the tunnel, extending forward, and I don’t know where they lead.

While Su Yuan used his spiritual thoughts to investigate the tunnel, he and Yu Baiying moved forward step by step.

After walking for at least twenty minutes, the two of them walked out of the tunnel. Strangely, the road was smooth and they did not encounter any agencies or ambushes.

Outside the tunnel, there turned out to be a deep valley in the shape of an inverted funnel, narrow at the top and wide at the bottom. It was surrounded by tall and steep mountain walls, and was covered by dense vines and trees.

If Su Yuan and Yu Baiying hadn't walked along the tunnel here, it would be difficult for them to find such a hidden place.

"There is a door there, should we go in and take a look?"

Yu Baiying suddenly pointed to the diagonally opposite side of the valley, where a stone gate appeared.

"Don't go there yet, there may be an ambush in this valley!"

Su Yuan said this to Yu Baiying.

As soon as he finished speaking, he felt something moving above his head.

Su Yuan looked up and saw four ninjas in black, holding on to vines and swinging down like ghosts.

The four black-clothed ninjas moved as fast as apes. They grabbed the vines and swung in mid-air for a few times before falling to the ground one after another. Then they quickly spread out and surrounded Su Yuan and Yu Baiying.

The strange thing is that these four ninjas all hold strange-looking guns in their hands.

The gun looked like a large trumpet with a metal pipe, but there was no magazine.

The four ninjas holding strange guns stood opposite Su Yuan and Yu Baiying in a fan shape, and raised their guns and pointed them at them.

"This is a special electronic net catching gun. It is equipped with a metal net made of special alloy. Once it is entangled, it is difficult to break free. Xiaoling was captured by this kind of gun! We must be careful!"

Yu Baiying recognized this kind of gun and immediately reminded Su Yuandao.

Phew! Phew! Phew! Phew!

As soon as he finished speaking, the four ninjas holding electronic net capture guns pulled the triggers almost simultaneously.

Suddenly, four metal nets glowing with blue electric light were ejected from the muzzle of the gun, quickly opened in the air, and then roared towards Su Yuan and Yu Baiying.

With Yu Baiying's reminder, Su Yuan did not panic. Instead, he waved his hands, and a strong wind suddenly came out, instantly knocking away the four roaring metal nets.

Su Yuan did not stop. He moved and rushed towards the four ninjas who fired the electronic net capture guns.

Seeing that the situation was not good, the four ninjas quickly retreated.

How could Su Yuan let them escape? His feet suddenly accelerated, then he leaned over and grabbed a metal net that had fallen to the ground, and threw it directly towards them.

Su Yuan's method of casting the net was fast and accurate, and the four retreating ninjas were caught in the net at once.

The four ninjas who were caught in the net suddenly screamed and uttered a burst of Japanese language.

Although Su Yuan could not understand the Japanese language, he knew that those ninjas were probably calling for help.

Sure enough, following the calls of the four ninjas, something happened on the opposite side, and a disk-shaped aircraft flew out from the stone door.

That disc-shaped aircraft looked very much like the legendary flying saucer, but it was only the size of a sea bowl. It was covered with a silver-gray metallic luster, which should be its coating.

The top of the disc-shaped aircraft is dotted with a circle of small holes, shining with blue light.

This thing was very fast. It flew from the direction of Shimen to the sky above the heads of Su Yuan and Yu Baiying. It was about four or five meters high, hovering and making a strange buzzing sound. The sound was like an extra-large bee.

Amidst the buzzing sound of the disc-shaped aircraft, Su Yuan suddenly felt a vibration in his head, and there was a wave of dizziness and even nausea in front of his eyes...

Yu Baiying was even more unbearable. She covered her head with her hands and fell to the ground. She looked very painful, but she still gritted her teeth and reminded Su Yuan: "Be careful, this... this is an infrasonic aircraft, which can release infrasound waves that are lethal...

"

The sounds that humans can hear are sound waves in the frequency range of 20-20000hz, and those below 20hz are infrasound waves.

Since the oscillation frequency of infrasound waves is close to the rhythm of people's brains, or when it is equivalent to the oscillation frequency of human internal organs, the internal organs will resonate strongly and strongly stimulate the human brain, causing panic, madness and restlessness in mild cases, and shortness of breath in severe cases.

Fainting, complete loss of self-control, and even death may occur within a short period of time.

Moreover, infrasound waves cannot be heard by humans, so they are difficult to detect. They can even penetrate walls and other objects and attack hidden targets.

Moreover, infrasound waves are very powerful and can cause serious damage to targets.

According to this principle, the infrasonic weapons emitted by the research can have serious effects on the human brain and nervous system. In mild cases, muscle spasms, whole body tremors, and difficulty breathing; in severe cases, blood vessels rupture, organs deform, shift, and even rapidly

die.

Yu Bai recognized the disc-shaped aircraft in front of him as a quite advanced infrasonic weapon.

"Infrasonic aircraft!"

Su Yuan's face froze when he heard this. No wonder he was so advanced that he almost couldn't resist it. It turned out that this thing was difficult to defend against, and the enemy actually had such advanced infrasonic weapons!

"Hurry up and find a way to destroy this statue, otherwise we will all have to..."
Chapter completed!