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.