Terraforming - the megascale-engineering of a planet's surface to one more Earth-like - is now commonplace across the Solar System, and Pluto's is set to be the most ambitious transformation yet. Four billion miles from the Sun and two hundred degrees below zero, what this worldlet needs is light and heat. Through captured asteroids and solar mirrors, humanity's finest scientists and engineers are set to deliver them. What nobody factored in was a saboteur - but who, and why? From the start, terraformer Lucian is intrigued by nine-year-old Nou, traumatised to muteness after a horrifying incident that shook the base and upended her family into chaos. If he could reach her, perhaps he could understand what happened that day - and what she knows about the secrets of Pluto. For Nou possesses unspoken knowledge - something that could put a stop to the terraforming. But crippled by her fears, and unable to trust her family, there is no one she can talk to. Only through Lucian's gentle friendship does she start to rediscover her voice - and what she has to say will transform our sense of place in the Universe.