This fairy tale, full of humor and suspense, begins in a small town where preparations are underway for a theatrical performance. The play tells a local legend about enormous riches hidden deep underground. Many long to find them, but those who set out in search of them never return. The play features two sisters, Kačenka and Barborka, as well as Jakub, a musician and Barborka's jealous boyfriend. The theme of the play also attracts the miserly lord of the castle, Bořivoj Hájek z Hájku, who arrives with his brother Ignác, an eccentric inventor and researcher. And somewhere underground, near the real treasure, sit his three ghostly guards, passing the time by inventing all sorts of pastimes, which the Lord of the Underground does not enjoy at all. His patience will run out the moment the bored guards interfere with human destinies, because of a bet on how the love between Jakub and Barbora will turn out.