Sea levels have risen. Whole populations are on the move and Britain has a zero immigration policy. When a massive tidal surge floods London, teenage Mark flees the destruction to stay with his cousin Ashanti in the Great West Forest. But where does Ashanti go at night? Who is she meeting? Attempting to solve the mystery, Mark triggers a catastrophic chain of events; Ashanti disappears, her family's farm is confiscated and the lives of the young climate refugees Ashanti is protecting are plunged into danger.