A mysterious letter addressed to Wu Laogou, Wu Xie’s deceased grandfather, disrupted the retirement plan of the Golden Trio, i.e., Wu Xie, Zhang Qiling, and Wang Pangzi. The letter referred to a mysterious underground palace called "Comet" in Mongolia. The Golden Trio decided to explore it, only to get involved in an unimaginable adventure and encounter treacherous Mongolian bandits, the countdown to escape from the "Comet", the weird rules of the burial chamber, and the invisible entity… The Golden Trio had no choice but to take a leap of faith…