At the end of 2045, the apocalypse arrives. Lin Fan, a poor young man, dies a miserable death caught between floodwaters and bandits, but is unexpectedly reborn thirty days before the end of the world and binds himself to the “Apocalypse Sign-In System.” Armed with foreknowledge and supplies from the System, he pinches every penny, stocks up, renovates his rental apartment, and makes frantic preparations. On the day the disasters erupt, he rescues Zhang Ya, a wealthy woman trapped in an elevator who had been utterly out of reach in his previous life. The two cross the divide between their social classes and depend on each other amid ruins without water or electricity, where humanity has been lost. From dealing with greedy neighbors to teaming up against hordes of mutated beasts, from torrential floods to extreme blizzards, Lin Fan uses his intelligence and sense of responsibility to rise into a survival champion, while Zhang Ya sheds her spoiled ways and grows quickly. The surprises from System sign-ins, the laughs and heartbreaks of survival, all intertwine. Against the brutal backdrop of life-or-death struggle, they write an apocalyptic legend about holding on to kindness and protecting love.