Book excerpt: 'A wonderful, surprisingly delicate story about a teenager making her way home to Scotland in a world remade by climate change (aimed at YA readers but, like all good children's books, good for adults too)' Lucy Mangan, i Weekend In a world full of checkpoints and controls, can love and hope defy the borders? A searing, timely story, as arresting as it is beautiful. Imagine a world ... Where there are too many people on a too-hot earth and your only chance of salvation is to journey north. Where you must prove yourself worthy of existence at every turn, at every checkpoint. Where your instincts become your most powerful weapon - even more than the gun in your pocket. Where you find out what it takes to survive. An extraordinary story about survival and what it costs, about the power of small kindnesses to change everything.