Synopsis：In a futuristic sci-fi world, human habitats are divided into the resource-monopolized "Upper City" and the harsh, polluted "Lower City." Residents of the Lower City barely survive under strict regulations, sustained by a nutrient called "Pink Spring." To save his daughter Renmei, who suffers from a severe case of "Underground Fever," a Lower City father named Jin Han embarks on a perilous journey to the Upper City in search of the legendary antidote "the Source." After infiltrating the Upper City, Jin Han is shocked to uncover the ruler Olin's dark conspiracy behind its false prosperity: the "Red Spring," which grants the elite immortality, is actually refined by brutally draining the life force of the Lower City people. Jin Han learns that his scientist father, Jin Yan, had long ago hidden the "Ultimate Antibody" capable of neutralizing the Red Spring within Jin Han's bloodline, in an attempt to prevent this humanitarian catastrophe. Faced with a moral choice affecting the fate of all humanity, Jin Han abandons the idea of saving only himself, choosing to sacrifice himself to destroy the core hub of the oppressive system, foiling Olin's plot, and winning dignity and hope for a new civilization for countless people in the Lower City.