Deserted by his magic, Fionn Boyle, Storm Keeper of Arranmore, sees the island beginning to wither and illness sweeping the land and must find a way to summon Dagda's army of merrows.
Fionn Boyle, terrified of the sea, must spend the summer with this older sister, Tara, and their grandfather on Arranmore, an island that has been known to make people disappear, and seems to be restless again.