Ozu skillfully operates a micro-drone to search under the cliff, this guy's control skills are good, and it seems that he has been playing for a long time. The country of sticks competes with Huaxia for everything, and even the ancestors have to rob it, I don't know if this drone will also follow the example of his eldest brother Mi Guoyan, saying that Huaxia stole their technology. Arrogance to a certain extent, the face is gone, like the American white-headed guy, who says that others steal him, and even though he is lagging behind others and says that others steal him, the most shameless thing in the world is the American white-headed guy.

"Dragon, I didn't find anything suspicious, this cliff is a knife-cut rock wall. Ozu said after controlling the micro-drone and scanning it twice with infrared light in front of the cliff.

"Why don't you check it out with the highlight light?" asked Xu San.

"It's not good, if this spare entrance and exit is under this cliff, even if no one is on duty, there will definitely be electronic monitoring. It's impossible to throw the back door here and don't look at it, a fool wouldn't do that. Xu San said.

"So what now? Do you want to dive and check over, maybe, the entrance and exit are underwater. "Longzi is a little troubled, since the cave is an exhaust port, then there must be a tunnel leading to the back mountain, there is no tunnel, how to lay the exhaust pipe?

But the question is, where is the exit to this tunnel? It can't really be underwater. If they were underwater, would they use submarines to transport secret supplies, or would all the supplies be waterproof and packed in and out of the water?

Is it really underwater? Is the fucking stick really such an elaborate entrance?

"I think it's better to go into the water and check it out. Long Zi said helplessly.

"Longzi, I have a way to investigate without going into the water. Ozu said suddenly.

"Tamma, there is a way to hurry up and say, if it succeeds, I will help me call five little girls when I go back to thin ears. Ryuko patted him on the back of the head and said.

"With ultrasonic detection, I have a micro-shaped ultrasonic detector in my bag, tie the ultrasonic detector to the drone with a rope, and then ....... Ozu said weakly.

"Haha, it's a good way, you said it earlier, hurry up, don't say it sooner if you have this thing. Ryuko slapped him on the back of the head again and interrupted him.

"This method, as long as there is no door to the entrance, it must work, if there is a door, it is not necessarily. Ozu said weakly again.

"What do you say?" Ryuko couldn't react for a moment.

"This ...... If there is a door, the reflected waves are the same, and there is no way to tell whether there is an exit or not. Ozu said quickly.

"Okay, don't treat me as an outsider, even if there is a door, because the inside is empty, the reflected wave is still different, you use the depth detection function, hurry up, or I will knock your head." Ryuko was very excited.

Soon, no one re-released, and the probe had just launched into the water and had not flown a few meters before it found an abnormal waveform, and from the waveform, it was found that there was a hollow place on the rock wall. The drone flew back and forth twice, and the detector swept back and forth at a low depth, getting two waveforms.

"Put it away, put the probe vertically, and probe the depths of this water. "Long Zi is very anxious, judging from the waveform, the empty place must be the exit, but the exit is underwater, and there is a door to block it, it is estimated that it is difficult to enter, otherwise, the base will not send people to guard.

Put away the drone, turn the ultrasonic wave of the lateral probe into a vertical probe and launch it again, and after a while, the depth map under the cliff came out. The water is so deep, I don't know what age this cliff was formed, the underwater cliff wall is so straight that the deepest place is ten meters deep.

"Brother Long Zi, judging from the waveform, this place has very few echoes, forming a square gap, I think that there is an almost square cavity here that should be the entrance. Ozu said, pointing to the waveform on the tablet.

"How do you think this is the entrance? Hollow cliffs, or other caves passing through here?"

"If it's just a hollow, it's also very deep, and the detection distance of this detector is 100 meters. You see, the waveform of this place is almost broken, that is to say, except for a little reflection on the wall, the waveform after passing through the thin wall, there is almost no echo, that is, the hollow is a hundred meters away, well, even if the sound wave is lost after passing through the thin wall, even if half of the loss is good, the space behind the wall is more than fifty meters. Behind such a rocky cliff, what is the reason for such a large cavity to naturally form?"

"Well, can you know what the thin wall is made of, and if this is really an exit, what material will this door be made of? Judging from the waveform, there is no depression here, is it? In other words, this door is in the plane of the rock wall?" said Ryuko.

"Yes, it's flat, and it seems to me that it's made of stone. They did this to disguise that it was a rock wall. Judging from the draft, half of this outlet is on the water at high tide. Therefore, his disguise is very necessary. Ozu analyzed.

"Okay, you're all right, do you have any way to get in?" Ryuko wanted to see if he had any good plans, but he couldn't think of any good plans, and there seemed to be no other way than to blow up. However, if it is fried, it will definitely alarm the other party, and he does not want the other party to know that they have been here.

"It's easy to get in, but it seems difficult to get in without the other person's knowledge. Unless, someone opens the door for us. Ozu shook his head and said.

"You're just talking nonsense. Ryuko said angrily.

The exit is submerged under the water, and the geology here is a hard rock formation, if you want to enter from here silently, there is really no way, no wonder the dead stick does not even send a defender. Oh, maybe it's guarded, maybe there's a big stone hall not far inside, where there will be a lot of supplies and escape utensils, maybe someone will be guarding it for a long time.

The alternate entrance arrived, but it was not possible to enter, which was really frustrating.

If you forcibly blow up and enter, unless you want to attack and rob hard, this way will not work.

What should I do?

Longzi called Zeng Beiping for instructions, but Zeng Beiping also had no idea for a while, so he asked them to withdraw to the villa first.

"Third Brother Xu, I think it's better to go down and have a look. This door is a backup emergency entrance, which can be opened from the outside. When he was about to return, Ryuko said very unwillingly.

"If it's just for escape, it may not be able to be opened from the outside. However, if this is also a secret material, it is very likely that it can be opened from the outside. Xu San thought for a while and said.

"Stupid, I'm sure it can be opened inside and out, but it's opened by remote control. Once again, Ozu expressed his opinion.