The protagonist is reborn 100 days before the apocalypse. He spends 300 yuan at the flea market to buy an abandoned copper key, which unexpectedly opens an ancient mechanical city sleeping underground. From then on, he stocked up on goods, upgraded the mechanical city, and gathered strong men. During the global catastrophe, he went from a little person who was trampled to death to a counterattack to become the city lord of the new civilization.
