In the 1970s, a research team led by Professor Yang ventures into a remote mountain region in China to investigate mysterious fossils. Among the team members are Hu Bayi, a young soldier, and Professor Yang's daughter, Yang Ping. They stumble upon an ancient cavern filled with strange, massive skeletons and relics. During their investigation, a catastrophic collapse traps the team underground, where they confront supernatural forces and otherworldly creatures.

As they struggle to survive, Hu Bayi begins to uncover a long-forgotten legend connected to the ancient relics and skeletons. Meanwhile, bonds are forged and shattered among the group, and secrets about the past are revealed. The survivors face even more perilous challenges as they seek a way out of the labyrinthine tunnels while contending with the ghostly tribes that haunt the area. Their journey is fraught with danger, mysticism, and revelations that forever alter their understanding of history and their own lives.