There is a huge underground cavity 1,200 meters underground on the Inner Mongolia Plateau in northern China. The Japanese went so far as to build a dam and a simple airstrip underground. A strange flight video left by the Japanese more than 20 years ago is just a glimpse of the cavity, but it reveals a lot of incredible information. What is there? Why didn't the Japanese in the brigade come back, and what happened to the lights under the void?
This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.
