A week has passed since Fionn faced Morrigan on the shores of Arranmore and said goodbye to his grandfather. Now Morrigan's brothers stalk the island in search of anyone with the power to threaten them, whilst the Merrows struggle to keep the growing forces of Black Point Rock at bay.
And in an unknown layer of the island, an enchanted oak tree lies hidden, protecting the knowledge of Dadga's grave - the tomb of the last sorcerer. For Fionn, Shelby and Sam, Dagda is the only hope of defeating Morrigan. The race is on to find him before it's too late.