The Great Cataclysm is over and humanity is gradually getting back on its feet. Army medic Daniel Manston has already been executed once for a crime he didn't commit, and now he's determined to stay alive. But to do so, he must solve a centuries-old riddle about the relationship between the sea people and humanity. On the remote arctic island of Svalbard, he finds an ally in Deryn, a female hermit whose task is to transcribe records of the ancient past. Together, they stumble upon a terrible truth that changes everything - and puts them both in mortal danger.