There is a string of lamps in the tunnel, but Cassia did not turn it on. Cassia, who is nearly three meters wide, is flexible enough to deal with it in the dark. The sense of direction has become Cassia's most sensitive perception at the moment, and her steps have been kept in the middle of the tunnel. Every time she deviates from the direction, Cassia will completely record it in her head so that when the detection is completed, she can draw a roadmap that is not much different from the actual situation.

With an air circulation system connected, the sound wave pulse detected some air transport pipelines. It was not turned on at this moment, and the tunnel seemed a little dull. If you use biological poison here, while running, Cassia suddenly thought that mixing into the air and getting great results without the enemy being prepared.

I don't doubt that when the air circulation system was built, or that others did not think of this. I didn't say it clearly, maybe I still have a wary attitude towards protectors like myself. The transportation team can be leaked, and they are also senior leaders within the organization. It seems that anything can happen in this period.

The tunnel is roughly a straight line, the curve angle is very large, and the perceived acuity is slightly lower, and this change may not be felt. And in the middle of the tunnel, Cassia also found a fork intersection. The other route is of course a dead end, with many sensing equipment installed inside, and the sound pulses found their outline. When they reached the cavity at the bottom of the route, the moving tool of the minecart was somewhat specified by the analysis machine.

I don’t know whether these forks are used to prevent enemies or to test warehouse management protectors like myself. In the case of Adolf and No. 5 who have left, it is easy to guess that such a task is probably used to increase the reasons for promotion and certainty to some elites. Just like when you have the opportunity, even if you only help hand over a cup and other tools, you can still put your own name at the end of some important research results.

In less than four minutes, an underground semicircular cavity with an area of ​​nearly 100 square meters was fully exposed and appeared in Cassia's perception. After a few breaths, Cassia, who was standing at the entrance of the cave, confirmed that there were no extra detection equipment around it, and then entered the cavity.

The size of the three-story building, the tracks in the tunnel extend to the center of the cavity and suddenly cut off. There was nothing around except air. On the side, as No. 5 said, several fixed beams of a lift penetrated the cavity from top to bottom, and two alloy safety doors cut off them, leaving only a section containing the cavity.

Cassia walked to the safety door, looked up and down, and then the high-frequency sound waves were emitted, penetrated the safety doors and detected the top and ends of the elevator.

"The upward approaches one hundred meters to reach the ground, the downward depth is nearly two hundred meters, and there are three safety doors in the middle to reach the bottom." Following the shaft of the elevator, the high-frequency sound beam slowly concentrated in one direction with consciousness. "There is an unloading platform at the bottom of the shaft, and there is also a simple hand-pushing cart, which is also a cavity structure. A door connects this cavity, and behind the door is,,,"

Cassia closed her eyes, and her highly concentrated spirit seemed to suddenly leave her body, appearing directly under the shaft, standing in front of the alloy gate with the teeth. The frequency of the sound wave suddenly increased by two or three levels, entering the third stage, and completely analyzed the changing structure at the throat. Where is the upper limit of the high-frequency sound wave? Cassia has not yet conducted a systematic test.

As the sound beam moves, the alloy door gradually fades into Cassia's head like a layer of transparent air. A wide underground building appears before Cassia's eyes. It is only a small part, almost like a fishbone distribution. In the numerous rooms, most of them are equipped with equipment and machines at the application. From the faint vibration feedback on their bodies, we can know that most of the observed machines are operating.

But he didn't see the researchers in the laboratory base for a while. Cassia tried to increase the frequency again, but in front of him, several glass test tubes placed on the bracket burst open. As if he was hit hard in his head, Cassia immediately stopped detecting and returned to the cavity like sleepwalking.

Without any words, Cassia subconsciously lowered her heartbeat and breathing, turned around and hid into the tunnel according to the original route. After three and a half minutes, Cassia, whose face had not changed at all, returned to the basement warehouse again. There was no one around, and upstairs, the other three were doing their own things in their rooms, and they didn't know what was happening here at this moment.

Nothing happened, Cassia slowly returned to her room and sat on the bed with this feeling. After a while, about half an hour, there was no contact sound from the communicator in his ears. Cassia let out a heavy breath: "We have to find opportunities and time to study the changes and applications of high-frequency sound waves in the third stage."

"Have the record been taken?"

"The assistant goes to print it, come over immediately." Shortly after the reply sounded, a knock on the door came. After a word of "come in", the door was opened, and a thin man with glasses stood at the door, walked in with three fingers thick paper in his hand, and placed it on the table in front of the three people in the room.

"Here are all the monitoring records, all converted into pictures, and the frequency is recorded every five seconds. I chose the time period within five minutes." The thin man's words did not fluctuate in tone, like a simple and cheap repeater, repeating the boring tone. "I discovered this in the past, Professor Mosil."

The thin man said as he pulled out two sheets of printing paper from the bottom of the stack of paper. The warmth was not lost yet, and the ink seemed to have not yet dried out, and the smell instantly spread throughout the room.

"The several rooms there were oscillation rooms, and there was a sudden record of ultrasonic waves of varying frequencies on the monitors in each room. Especially the record in the test tube fragmentation room is the highest."

But Professor Mosil said "Oh", took the record form on the thin man's hand, and asked: "In terms of time, the two should be completely overlapping, right?"

The thin man nodded, "It's totally coincidental. The machine we used has checked and there are no faults. The records in the analysis machine have also been viewed. Since yesterday, there have been no records of calling and opening. It is very certain that the test tube is broken because a sudden high-frequency sound wave shattered it, but the source of this sound wave,,,"
Chapter completed!