Lydia, the miller's daughter, teaches herself bookkeeping and, thanks to her extraordinary mathematical talent, seizes the opportunity to be hired as the estate's steward. Facing her colleagues' criticism and the many trials of estate affairs, she holds to her principles and skillfully resolves trade disputes among neighbors. During joint cooperation with a neighboring estate, she and the East Estate's heir Estan fall for each other, finally achieving fulfillment in both career and an equal love.