In a year of disaster and famine, a young girl named A Tang climbs the mountain to gather wild vegetables and saves the Black Wolf King, the mountain guardian, who is trapped on a cliff and seriously injured. In gratitude, he gifts her a Hundred-Grain Stone Mill capable of producing food. A Tang follows his warning faithfully, using the mill only to help villagers on the brink of starvation and never exploiting it for personal gain. But the treasure attracts the greedy wealthy landlord Liu, who plots to steal the mill and turns the villagers against A Tang. The mill refuses to obey an evil person and transforms into sandworms in the Liu household, shaking out their enormous hidden grain reserves and illegally seized land deeds, exposing all their misdeeds. After the turmoil, the mill remains in the village, helping only those in desperate need. Rain falls, crops grow, and the hundred grains flourish. The Black Wolf King returns to guard the northern mountain, and A Tang's kindness ultimately brings peace and a secure livelihood to the village.