It is the turn of the 20th century, Ireland, when a young boy – William Muldoon – happens upon a friendly Grogoch who shows him to his mythical home underground. There he meets the Dwelvin-Mites; a community of Imps whom he’d always been fascinated by through story.
His fascination soon wanes when their beautiful guide, Anun the Creator, explains to him how they are in hiding from an evil tyrant – a Wrythunn warrior and Pooka named Drevol Briggun – who has seized their subterranean home of Lythiann and how it is up to William to assassinate him, being the reincarnation of the only other Wrythunn in existence who has the potential to confront Briggun’s power. What’s more, a curse has been placed on William’s home, and the only way for it to be reversed is upon Briggun’s death.
With little choice in the matter, William takes to the seemingly empty world of Lythiann to carry out this frightening task, only to discover that it’s not as uninhabited as he first believed.
Singly joined by a friendly rabble, he learns more about himself, his past, his future, and how his transformation into the great Wrythunn warrior, Mysun Margyle, will not hold true without the Symphogram; a gramophone-like device which performs Mysun’s mighty theme. A composition known as the Banádh.
For this to happen, he needs to truly understand his cause, which isn’t as easy as he once thought.