The game begins with you awakening from a long slumber underground. You find yourself in the rubble of the destroyed city of Zenith. A young engineer called Catherine found you and managed to reboot your AI. As you follow her back up from your grave site to the surface you learn about her new settlement that was established above ground -- the first to try doing so since the calamity wiped the surface clean. As the game unfolds you help this new settlement survive. In doing so you venture deeper and deeper underground through a wide net of tunnels, caverns, and abandoned structures to find the last few remnants of humanity.