"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...When Mirin's grandfather dies, her grandmother puts in...a plan to restore their glory - but at the price of Mirin's freedom"--,Provided by publisher.