The eternal night and a deadly cold wave descend upon the world, while the boiler in Black Iron City is on the verge of collapse. Lu Yan, a maintenance worker, escapes the crisis with a mute uncle who has a crippled leg. They find an abandoned geothermal well and struggle to survive. They build defensive fortifications, learn to ration their supplies wisely, and rescue large numbers of fleeing survivors. Facing a siege and suppression by villainous forces, Lu Yan relies on his technical expertise, evidence, and the strength of the people to stand against tyranny and uphold the principle of fair survival. After enduring attacks from giant beasts and power struggles among various factions, they abandon their old home, board a mobile fortress, and head south in search of new land where they can farm and settle down.