This is one of the stories from Andrew Lang’s, Orange Fairy Book, published in 1906. This story is in the public domain.
The original title to this story was The Rider of Grianaig, and Iain the Soldier’s Son. It is a Scottish fairytale that was collected by John Francis Campbell and written down by Hector MacLean in 1859. Andrew Lang included it in his Orange Fairy Book in 1906.
The story is about Ian, a young son of a soldier who must rescue not one, but three princesses who have been kidnapped and taken away to an island where they are being help captive until they agree to marry three giants.
I admit this is quite an odd story, but if you would like to read it you can find it and other stories at Project Gutenberg.
If you would like to listen as I read the story to you, click on this link. The running time for this tale is 28:59.