I can't go back in the house. I'm restless, prickling all over. The wind hits me like slaps from huge invisible hands. But it's not the wind that worries me. It's something else, beyond the storm...

Sapphire and her brother Conor can't forget their adventures in Ingo, the mysterious world beneath the sea. They long to see their Mer friends once more. But a crisis is brewing far below the ocean's surface, where Saldowr, the wisest of the Mer, guards the Tide Knot. And soon both Sapphire and Conor will be drawn into Ingo's troubled waters.