Artemis Fowl by Eoin Colfer
"Irish businessman will pay large amount of U.S. dollars to meet a fairy, sprite, leprechaun, or pixie."
The ad was posted on the Internet. Indeed, it generated numerous fraudulent responses, but the person who placed it only needed one true lead for his purposes. He had studied all he could in the mundane world he inhabited, but he knew the important secrets of the Fairy would only be known by others of their kind.