What are Julia, Rosie and Sydney up to this time? Find out in Book 2 of the Dress-Up Detective series! This time, the girls are up for a wet, sea-weed covered adventure under the sea! The magical dress-up trunk delivers them to Mermaid Castle, where they must help the royal mermaid family discover who wants to ruins the the princess' birthday party! Someone has warned that a twister is coming. Who would cast an evil twister spell on the afternoon of a wonderful party? Help the girls find all of the clues! Can they solve the case?