In the future, the greenhouse effect will intensify, the environment will deteriorate, and people will be forced to move to underground cities. Underground energy is facing depletion, and scientists are working hard to develop temperature stabilizers, hoping to lead everyone back to surface life. howeverOn the day of the gas emission experiment, a toxic gas leak occurred, and the underground Mordo lizard mutated into a giant beast, wreaking havoc. Disaster struck.... People have to take the only train that leads to the surface and escape from dire straitsJourney.