Determined to live her life as normal, Cleo confronts her fears and lands a job at the Marine Park, helping out to feed the dolphins. Despite her precautions, she gets splashed and, just as she's about to turn into a mermaid, a mysterious Old Woman, Miss Chatham, comes to her rescue. Cleo is certain Miss Chatham knows more than she's letting on. Meanwhile, out exploring the Moon Pool at Mako Island, Emma find a necklace; more proof that the girls are possibly not the first to have been there. Also determined to live a normal life, Emma goes ahead with a sleepover party. When Cleo is splashed at the sleepover, Cleo has to hide in a closet before she morphs. Cleo is revealed to the party – as a mermaid but in her sleeping bag! After this, our girls realise life will never be the same.