Book excerpt: Utterly's mother turned and came gliding back between the sunbeams. 'Swim with me, Utterly,' she said. 'I have so much to show you.'Utterly Dark has made a promise - to leave everything she's ever known, and to go and live in the sea with her mystical, oceanic mother. Leaving home is difficult enough, but soon Utterly learns someone is hunting her. Someone - something - from, incredibly, a different time.Utterly will have to delve to the ocean's magical depths, swim through impossible timeslips and face painful choices if she is to save herself, and those she loves . . .A magical new story from the bestselling and prize-winning author of Mortal Engines.