When Scottie realises that she may never become a mother, she makes the heart-breaking decision to flee to the remote North Atlantic archipelago of St Hia. Lashed by storms and far from the mainland, the islands are dangerous. Many have been lost to the ferocious tides known as the Hollow Sea – and local folklore warns that St Hia was once the home of a witch. Her name was Thordis, and when she was unable to provide her husband with a child, she was driven to a terrible act. The islanders warn newcomers against examining the past, but Scottie can’t look away from the mystery of what happened to Thordis. Could it be that St Hia’s troubled history holds the key to Scottie’s future?