A girl who never knew her father. A secret hidden deep beneath the waves...A sunny day on the Isle of Skye, a trip to the beach and a boat ride should have been the perfect relief from exam stress for Riva. Instead it leads to a tidal wave of events that pull her under the waves in pursuit of her long-lost father. Why does the ocean respond to her voice alone? Does the fate of the Mer, and the world, rest in her hands?

Returning to land after her dangerous voyage under the waves over the summer hasn't been easy for Riva. She may have saved her father from life imprisonment, but her uncle now wants her dead and the Mer have turned against her. To make matters worse, she now possesses the spirit and powers of Mother Nature with no idea what to do with them. Will she learn to control them before they control her?

Riva thought that saving the Mer was going to be dangerous enough - then she got involved with the Titans. After losing access to her magic during the battle of Oceana, and Gaia revealing her true nature, Riva is desperate to keep herself and her family safe by training with Cronos, but should she trust the Titan's motives? Has she placed herself and her friends in more danger? Or will she be able to save herself, and her heart, in the end?