The narrative begins at a picturesque cottage by a dark and enchanted forest, where an old fisherman and his wife adopt a wondrous, whimsical child named Undine after their own daughter vanishes into the lake. Years later, Sir Huldbrand of Ringstetten loses his way in the forbidden woods and finds shelter in the cottage, instantly becoming captivated by the capricious and enchanting Undine. Despite warnings about the forest spirits and the strange occurrences that surround her, Huldbrand marries her, which grants the elemental water sprite a human soul and the capacity to love deeply. As they journey to the knight's castle, complications arise due to Huldbrand's former attachment to the proud and ambitious Bertalda, whom Undine later discovers to be the fisherman's true lost daughter.
Despite Undine's gentle patience and unwavering devotion, Huldbrand's affection cools as he grows weary of her supernatural kindred and the strange portents surrounding them. Driven by temper and regret, Huldbrand harshly rejects his wife during a voyage down the Danube, causing Undine to vanish back into the river's depths to protect him from her powerful uncle Kuhleborn. Believed to be dead, Undine leaves Huldbrand to pursue Bertalda for marriage, despite warnings from the holy Father Heilmann about the perils of forsaking a devoted spirit.
On the eve of the wedding, Bertalda has the castle fountain uncovered to obtain beauty water, allowing the weeping Undine to return to the chambers above. Bound by the laws of her race, Undine bestows a fatal, sorrowful kiss upon the repentant Huldbrand, who dies in her arms. At his funeral, a mysterious silver spring emerges from the turf to circle his grave, embodying the enduring love of the forsaken Undine.
