Synopsis：A mysterious letter sent to Wu Xie's late grandfather Wu Laogou disrupts the retirement plans of Wu Xie, Zhang Qiling, and Wang Pangzi. The letter points to a "Comet" tomb in Outer Mongolia and the invincible trio decides to explore it, but unexpectedly gets involved in an unimaginable adventure. With the sinister Mongolian bandits, the countdown to escape from the "Comet" tomb, the unnerving rules of the tomb chamber, and the invisible "it”... The invincible trio has to give it a shot...