In the mystical realm of the Sidhe, the fairy folk of Celtic mythology, a power struggle threatens to disrupt the delicate balance between the Seelie and Unseelie courts. Aine, a young Seelie princess, finds herself caught in the middle when she falls in love with a handsome Unseelie prince. Their forbidden love could ignite a war that would devastate both courts and spill over into the human world. To prevent this, Aine must embark on a quest to retrieve the legendary Harp of Dagda, said to possess the power to restore harmony. Along her journey, Aine encounters various creatures from Celtic mythology, like the fearsome Banshee and the wise Druids. She also learns about the ancient Celtic traditions, their reverence for music and storytelling, and their belief in fate and destiny.