When Nell West starts extending her Oxford antiques shop, she is not expecting to uncover strange fragments of its past - fragments that include a frightened message scribbled on old plasterwork, dated 1850 and referring to someone called Thaisa. She also uncovers a mysterious link with a village on the Dorset coast - a village with an ancient bell tower and dark memories of a piece of music known locally as 'Thaisa's Song'. The sea is gradually encroaching...