It comes as a surprise when Carnuckelby, the Pebble Man, informs Swannie that she has to return to Amarvin Island to attend her own Dream-Day Ceremony, where a specific Task awaits her. The wellbeing of the island and the world will depend on the successful completion of this challenging mission. She realizes that without the help of her friends from school she might never succeed. However, she runs the risk of exposing her true mermaid self in the process. But help comes in many forms. Apart from Feliciana and the boys, there's Matmaka, the dolphin, who advises her, and Whooshyminne, Fitzeepire, and Lak-Nasheem from the realms of nature, who are always ready to support her. Furthermore, she makes the acquaintance of a mysterious new little girl at school. What role will she play? But will all this help be enough to overcome the trials they face?