Once upon a time, there was a poor fisherman. He lived by a wonderful lake, large and crystal clear as diamonds, but the fish grew small, and he found it more and more difficult to feed his family. Eventually, he was catching barely a fish a day, and he knew that if this continued, they would starve before the next spring. One day, as he was fishing in his small boat, he heard a beautiful sound coming from the other side of the lake. Enchanted, he quickly rowed to the sound, where he found a handsome young man playing a violin so sweetly and sadly that the fisherman began to cry. "Now, now, fisherman," the boy sang, his voice as soft as velvet. "Why do you cry so?" The fisherman cried even more so and explained his troubles to the strange boy. He listened to the man's story, playing his violin as he did so. Finally, he put aside his instrument, and quietly told the fisherman that in three days his wife would become pregnant with a beautiful little girl, more lovely and charming than anyone else in the kingdom. He then told the fisherman that he would gladly give him great catches of fish to feed his family, but in return, he must give the boy his daughter when she turned eighteen. The fisherman hurriedly agreed, only thinking of food and the promise of fish. The young boy made him pledge in blood; when the oath was sealed, he slipped away into the forest and disappeared.
Sure enough, the next day, the fisherman was shocked to find that his nets were full of fish, and that each one was fat and healthy. He realized in horror that the young man he had met was a nix - a beautiful water spirit who lured demon and children to their deaths. He wept and wept, but refused to tell his wife of his bargain. Finally, he returned to the place where he had heard the nix play. "Please, spirit!" he cried. "Do not take my only child away! I beg you!" The spirit stepped out of the water - this time in the disguise as a merman. "We made a deal, fisherman," he said calmly. "I'm afraid you are too late. Your child is mine, now. Enjoy your time you have with her." And with that he slipped back into the lake, and did not appear to the fisherman again, no matter how many times he called. The fisherman grieved even more so, and ran home to confess to his wife the deal he had made. She only laughed at him - surely his old age was to blame for these illusions!
As the months went by, the fisherman slowly began to believe that what he had seen must have indeed been a trick, and so he was even more surprised when, precisely when the nix had said, his wife gave birth to the most angelic child, with hair a perfect chestnut brown, and her eyes as blue and clear as the lake. Still he refused to believe he had sold his innocent child to such a fiend, and they continued their lives as if nothing had ever happened. The fisherman caught bountiful fish, and the wife took care of their perfect daughter. And so, for many years, they were a perfect family, and forgot everything of the troublesome nix and their promise. And, during that time, they lived happily ever after.