There's a current racing ahead, the colourof the darkest blue velvet. We plunge forward.The current is so strong that it crushes me.I'm jolting, juddering, struggling in its grip,but I can't break away. It's got me, like a catwith a bird in its claws.Sapphire and Conof can't foget their adventures in Ingo,the mysterious, fascinating world beneath the sea. They long to meet their Mer friends Faro and Elvira again. But they've moved from their cottage on the cliffs, and from the cove which was their gateway into Ingo.Their mother wants to start a new life in the seaside town of St Pirans, away from the haunting memories of their father who disappeared at sea the year before. But a threat is growing deep beneath the surface of the sea, where the wisest of the Mer, Saldowr, guards the Tide Knot. Ingo is restless, and soon both Sapphire and Conor will hear the call of the Deep...