Antonia is a secret Silver Dolphin – she's responsible for helping the creatures of the bay when their environment is threatened, by responding to the call of her magic necklace.

It's the start of the summer holidays and Jessica, Antonia's sister, is becoming increasingly obsessed about 'catching up' with her big sister. She covets Antonia's necklace and cannot resist the temptation of borrowing it' Antonia is distraught when she thinks it's lost for ever: how will she hear the distress call of her dolphins without it? But they are not the only ones in need of her help…