Imagine a world in which every bad thought you had was made visible. Where anger, hatred and envy appeared as a thick, infectious smoke pouring from your body, leaving soot on your skin. A society controlled by an elite who have learned to master their darkest desires. Thomas and Charlie are friends at a boarding school near Oxford, where the children of the rich and powerful are trained to be future leaders. Charlie is naturally good, but Thomas's father was accused of a terrible crime, and Thomas fears that the same evil lies coiled inside him. Then, on a trip to London - a forbidden city shrouded in darkness - they learn all is not as it appears. So begins a quest to understand the truth about this world of smoke, soot and ash - and perhaps to change it. 'Mesmerising and imaginative ... a novel that tackles the most fundamental question of good versus evil' Hannah Beckerman, Observer 'Like an adult version of the Harry Potter books with a touch of Dickensian dystopia ...a sheer delight' Maxim Jakubowski, Lovereading 'A novel that stays in the imagination long after it is read' Adam Roberts, Guardian