There's a tale in one of my books of Swedish fairy tales that seems to have been popular in its time--it was written by a well-known author, illustrated by John Bauer, one of the great turn-of-the-century illustrators, and made into a children's opera. The story is Helena Nyblom's "The Changelings" (Bortbytingarna in the original). Nowadays it seems to have fallen out of favor, since it appears only in one out-of-print collection and one in-print collection, so I was surprised to find it used as a source in the Wikipedia article on changelings.

What I'd like to know is: Has anyone else heard of this story? If so, how common is it where you live?