Katie returns to her Aunt Flora's cottage in Cornwall, for her second summer holiday and where she again meets Katie her mermaid friend, who is the keeper of the magic camera.Amy is thrilled that her best friend Jessica from her school in Scotland has arrived to stay with her.The three girls travel to a castle hidden in a secret garden to find Princess Isabel; the love of Herman, who has a spell hanging over him, sent by Cordren, the witch, who interferes in Amy's family life. Amy still hasn't found the connection between Katie, Cordren and herself, but there is one, will Amy find it in this adventure?As last summer, there are battles to win, even between Aunties cat, Sandy and the witches cat, Darkness, after Amy and her friends find themselves trapped in Cordren's den, beneath the castle.Will the girls find the Princess and escape from Cordren?