Around AD 2400, the natural environment suffered a collapse disaster. The polar ice has melted in large areas, the fertile soil has turned into sand, and energy has been exhausted. Humanity relies on limited technological means to survive. However, what is more deadly than natural disasters are the giant mutated rats that have evolved terrifying intelligence. They occupy the surface of the earth and compete with humans, forcing humans to create underground cities and begin the humiliating "Cave Era."
Just as the underground city was struggling to expand, a strange event happened: the high-speed subway was torn in half by some unsolvable force. At the scene of the subway accident, a bottomless cave suddenly appeared. It is not like the scar of a disaster, but rather like a specially sent "invitation", waiting for human visitation.
In order to reveal the truth of the incident, senior scientist Connie personally led a top-secret team into the abyss, determined to advance forward, and experienced a series of incredible and strange encounters, all the way down to the death zone of the crown of the mantle, which is 400 kilometers deep, kicking off the encounter between the two civilizations...
