The miller had always led a very prosperous life, but one day found himself down on his luck and without any money. While he is fretting, a nixy (a siren-like being) emerges from the mill-pond and strikes a deal with him – he can become prosperous once more, but he must give to her the youngest thing in his house. He agrees, thinking it will be a puppy or a kitten, but soon discovers his wife has just given birth to a son. Greatly despaired, he tells his wife of the bargain he has just made and they work hard to keep his son away from the mill-pond his whole life. After the son marries, he finds himself at the mill-pond one day and the nixy takes him. His wife then goes on a long mission to recover her husband.
Andrew Lang (1844-1912) was a Scottish writer who collected fairy and folk tales from various cultures and put them together in twelve volumes of tales. He was noted for taking the tales from as many original sources as possible, keeping the fairy tales close to their intended meanings.