The imperial councilor Ullik decides to modernize his old mills by installing a new turbine. His eccentric brother-in-law Artuš tries to prevent this, as the construction work disrupts the statics of the tower in which he lives. Ullik's older daughter Tynda is a talented singer. The bewitched girl secretly accepts the courtship of the virile Václav, the son of the night watchman. Her younger sister, the doctor Marie, wins the heart and hand of the astronomer Zouplna, despite her father's prohibition...
