A number of other operas and ballets have been based on Fouqué's version of the myth of the water spirit Undine, including Tchaikovsky's Undina, E. T. A. Hoffmann's Undine, Cesare Pugni's Ondine, ou La naïade and Hans Werner Henze's Ondine.

Hugo and his squire Veit have been forced by bad weather and floods to take refuge in a fishing village, and have been living there for some months.

Hugo has fallen in love with the beautiful Undine, the foster daughter of the fisherman Tobias and his wife Marthe, and plans to marry her.

He decides to watch over Undine and accompanies the young couple and Veit to the imperial capital, disguised as a priest.

The winemaker Hans is happy to welcome back his drinking friend Veit, who tells him about his adventures, and that he has married Undine, a mermaid without a soul.

As she reviles Undine because of her lowly origin, Kühleborn claims that Bertalda is actually the child of fisher people, who she contemptuously rejects.

Veit and Hans, who has entered into Hugo's service, celebrate the wedding of their Lord with Bertalda, which will take place that day.

During the marriage celebration in the castle hall, Hugo, in vain, seeks to dispel ill forebodings.