Mike has a licence to move tourists through Tion's spheres, despite new restrictions in the movement of people and data. His latest clients know nothing of his previous life and relationship to Pazel, or of the voice from his past, tempting him to return. When Mike discovers scattered communities across Tion's exposed surface, he knows he must confront Pazel. As they descend into the Depths and beyond, the crisis facing Tion becomes clear: the oceanic ice starts to bombard the world. Their journey becomes one of survival, not just theirs, but for hundreds of thousands of billions of consumers.