With the help of some mysterious crystals, Thora the half-mermaid brings a special sparkle to her third and final adventure ... She and her family have reached the shores of Flinders Island near Tasmania, the birthplace of Cosmo, her pet peacock - but what has happened to his relatives? When Thora's guardian, Mr Walters, has trouble with his back, he and Thora end up at the nearby Deep Breath Hotel and Spa - where Thora lands her first job minding bratty Felicity, the daughter of the hotel's owners. But there's something not quite right about Felicity's parents - or Mr Walters. He takes up yoga, swears off his favourite foods and isn't even interested in cricket! Does a bath in Felicity's house full of sparkling crystals have anything to do with it? When Cosmo goes missing, Thora must use all her half-mermaid skills to get to the bottom of the mystery - and the solution will affect her in a way she could never have imagined!