Saoirse is a child who is the last of the selkies, women in Irish and Scottish legends who transform from seals into people. She escapes from her grandmother's home to journey to the sea and free fairy creatures trapped in the modern world.

Young Brendan lives in a remote medieval outpost under siege from barbarian raids. But a new life of adventure beckons when a celebrated master illuminator arrives from the isle of Iona carrying an ancient but unfinished book, brimming with secret wisdom and powers. To help complete the magical book, Brendan has to overcome his deepest fears on a dangerous quest that takes him into the enchanted forest where mythical creatures hide. It is here that he meets the fairy Aisling, a mysterious young...