Cowrie can't anticipate the chemistry that will begin when a group of traditional storytellers sets off to the Orkney Islands with Ellen, to stay at her coastal family cottages. For Ellen turns out to be Morrigan, and Morrigan is a selkie, living in the sea and on land. As an ancient mystery unravels, Cowrie and Sasha must turn detective to discover the truth behind Morrigan and the song of the selkies.