The story usually goes as follows: a knight or king finds a beautiful and mysterious maiden in the woods, often near a stream or spring. They marry on the condition that he gives her one day out of the month, or week to spend alone bathing. He cannot look at her during this time, or speak with her. Things go on happily for a while (usually several years) and they have many children together. But then one day the knight or king's curiosity gets the better of him, and he peeks in on her bathing. He sees her in her true form, half woman on the top, half fish or reptile below the waist, and is greatly disturbed. She leaves with the children never to return.
Here's an illustration from the German translation of the Melusine legend by Thuring von Ringoltingen.
|Melusine, Thüring von Ringoltingen, 1456, Germany.|
For a more in-depth read about Melusine, the legends, and etymology of the name, check out this post on the Origins: What Does History Say? blog.