The causeway shuts at a quarter past five. After that, the sea decides. Forensic accountant Edie Stannard has not been home in sixteen years. When her mother drowns in a drainage dyke on the Norfolk marsh, Edie goes back to Saltreach for one reason: to sell the cottage and leave. But her mother kept books, and the numbers in them do not add up. A village that rings its own tide bell. A ferryman who walks in his sleep. A committee that has kept the sea out for seventy years and wants very much to go on being thanked. Every figure Edie checks leads to another one she was never meant to see. Some debts are paid in salt.