A knight named Huldbrand comes across a fisherman's hut in the forest, and is welcomed in by the fisherman and his wife. He also meets their capricious eighteen-year-old foster daughter, Undine. The fisherman explains that years ago, their young daughter was lost in the lake and apparently drowned, but that same day, Undine appeared on their doorstep. Since then, they have raised her as their own. Undine asks Huldbrand what he is doing in the forest. He explains that he was participating in a tournament when he met Bertalda, a duke's foster daughter. As they flirted, she promised to give him her glove if he would explore the haunted forest. He did so, encountering strange and threatening spirits until he reached the fisherman’s home. A storm arrives and a flood surrounds the house, stranding the group. During their time together, Huldbrand and Undine fall in love, although she continues to behave erratically and can seemingly control the weather. An elderly priest, Father Heilmann, arrives after being washed overboard from a ferry. Huldbrand suggests that the priest marry him and Undine, and they hold the ceremony immediately. The morning after the wedding, Undine suddenly acts like a completely different person, kind and gentle. She explains to Huldbrand that
elemental beings exist and she is a
water spirit. Her species does not have immortal souls or any sense of morals, but can gain them by marrying humans. She was sent to live among humans by her parents, who hoped she would earn a soul in this way, and with her marriage to Huldbrand she has accomplished this. She fears that Huldbrand will leave now that he knows what she is, but he swears never to abandon her. With the flood receding, Huldbrand and Undine depart for his home. On the way they encounter Kuhleborn, a shapeshifting water spirit and Undine's uncle. She is now frightened of him and begs him to leave, and Huldbrand tries to attack him, only for Kuhleborn to vanish into a waterfall. In the city, everyone welcomes Huldbrand back. Bertalda is deeply disappointed when she learns that he is now married, but becomes friends with Undine. One day, Kuhleborn visits Undine briefly, warning her of Bertalda. She rejects his warning but reveals at dinner that he told her who Bertalda's true parents areUndine's own foster parents, the fisherman and his wife, whom she has brought to meet her. Bertalda is the child who they believed had drowned. Instead of the joyful reunion Undine expects, Bertalda feels humiliated to realize that she was born a peasant. She publicly reviles them and calls Undine a witch, but her identity is proven by her birthmarks. Bertalda’s behavior causes both her foster parents and biological parents to disown her. Destitute, she begs Undine for forgiveness. Undine immediately takes her into her home, but Bertalda remains fearful of her, and Huldbrand's attraction to Bertalda resurfaces, leading to tension. Undine orders the servants to seal up a fountain in their castle’s courtyard. Bertalda, who uses the water for her complexion, argues with her and complains to Huldbrand. He harshly demands an explanation. Undine explains that she is protecting their home from the malicious Kuhleborn, who would be able to enter through the fountain. She then asks Huldbrand never to speak angrily to her while they are near water, or her relatives will take her away. He contritely agrees. Bertalda flees the castle in shame, and Huldbrand goes to rescue her. Kuhleborn, in different forms, torments and tricks the pair. He is about to drown them with a flood when Undine arrives, calms the waters, and carries them to safety. The three live in peace for a while, until they decide to take a trip along the
Danube to
Vienna. While on the river, Kuhleborn continually torments them with storms, waves and frightening apparitions. The sailors and servants become suspicious of Undine as she magically stops these attacks, and Huldbrand begins to resent her. When a water spirit steals Bertalda's golden necklace, Undine immediately offers her a coral necklace to replace it. Seeing this as a sign that Undine is colluding with the spirits, Huldbrand throws the coral necklace overboard and accuses her of being a sorceress. As she predicted, Undine disappears into the river, but not before sadly warning him to remain true to her. Huldbrand grieves her loss, but as time goes on, decides to marry Bertalda. He even asks Father Heilmann to perform the wedding, but he refuses. The priest has received messages from Undine and cautions Huldbrand against breaking his wedding vows by taking another wife while Undine still lives. Huldbrand himself dreams of Undine and Kuhleborn talking beneath the sea, saying that if Huldbrand marries another, Undine will be compelled to kill him. Undine says that she has protected the castle by sealing the fountain, so no water spirits including herself can go there, but Kuhleborn points out that Huldbrand will be doomed if he ever unseals the fountain or leaves the castle. Despite these warnings, Huldbrand continues with the wedding. Immediately after the ceremony, Bertalda wishes for water from the sealed fountain. The servants uncover the fountain, only for the veiled and weeping Undine to rise from it. She enters the castle and kisses Huldbrand, drowning him with her tears. She appears once more during his funeral and transforms into a stream encircling his grave, so that she is eternally embracing him. == Inspirations ==