Nuclear winter descends, civilization collapses, and humanity is no longer the master of the world. To protect themselves, humans have built one fortress after another, while beyond the walls, survival comes only through blood and fire. Ren Xiaosu and his younger brother Yan Liuyuan are among those left outside. Once ordinary boys of the wilderness, they have no shelter and nowhere to run. The only thing they can rely on is each other. When a massive earthquake strikes Jingshan, Fortress 113 comes crashing down, laying bare the chaos of the post-apocalyptic world. During their escape, Ren Xiaosu and his family rescue Luo Lan, a military leader, and make their way into Fortress 109. A new life seems about to begin, but the real trials have only just started… (Source: Bilibili TV)