Life is trouble-free on Mako Island – until Ondina meets Weilan, a mermaid from the Eastern pod. They immediately clash and Mimmi must act as peacemaker. But a greater threat to their peace has arrived, in the form of a fearsome Chinese water dragon that once destroyed the Eastern pod. But the dragon is not all it appears to be. On their perilous quest to defeat the dragon, Zac and the mermaids discover shocking secrets until a final confrontation reveals all.