Before the advent of the undertide era, an ordinary middle-aged woman had a strange experience:
For nearly a month, a saying has been circulating in this city: Once you enter that strange cave, your life will be completely changed.
The dark figure squatting in the corner in the middle of the night, the strange shape in the mirror, an invisible person living at home, the mysterious creature accidentally caught by the camera in the forest, the child disappearing out of thin air on the playground...
There may be more than one human civilization on this planet, and when people die, they may not really die, but just change their way of existence. Everything is possible.
Purpose: Remain in awe of the unknown