The UK is flooded, and the world has become a global disaster zone. Order has broken down, and the systems that all society had relied on have collapsed. NOAH - a group of vicious and powerful religious extremists - emerge to rule with terrifying violence and archaic notions of oppression. Anna and Robbie flee the water plains of London and become refugees, alongside millions of others, making their way north. They take the perilous journey to join a small and remote community in a Cumbrian watermill. While they find solace and solidarity in the group, their safety is soon put in jeopardy by the arrival of a desperate stranger and her children. When people begin to go missing, Anna must use all her powers of trust, love and resilience to save her friends and the man she loves.