Rosie finds a beautiful spiral shell in Great-aunt Rosamund's castle and notices that it has young girl looking anxiously towards a smoking volcano drawn on it. Rosie drops into a curtsey and says hello. All of a sudden a gust of wind surrounds Rosie, full of sea spray and smelling of pineapples and hibiscus flowers.
When Rosie opens her eyes it's sunrise and she finds herself sitting in a canoe that is being pushed down to the sea by Princess Kalia. The little princesses's tribe is in great trouble because the volcano on their island has woken up and is threatening to erupt at any moment. Kalia is setting off to find the magic shell of the Eppa people, for only the beautiful sound it makes when it is blown will put Pele the volcano goddess to sleep. Rosie says she will help her new friend and off she goes on another exciting adventure!