Orphaned as a young child, Mirin O’Malley has been brought up by her grandparents on their isolated, rambling estate Hob’s Hallow.
Long ago her family prospered due to a deal struck with the mer, the terrifying creatures who live in the depths of the sea: safety for their merchant ships in return for a child of each generation. But for many years the family have been unable to keep their side of the bargain and their fortunes have suffered as a result. When Mirin’s grandfather dies, her grandmother puts in train a plans to restore their glory – but at the price of Mirin’s freedom. Finding amongst her grandfather’s papers evidence that her parents may still be alive, Mirin is determined to escape and discover the truth about her origins.