Instow, Devon, 1873. Early in the morning, the body of a chambermaid is discovered on the beach. Abigail March and detective Theo Newton are among the hotel guests. The cause of death is certified as drowning, but Abigail is immediately convinced there has been foul play. Determined and clever, Abigail has completed her medical training but, being female, is barred from qualifying as a doctor. In spite of his fondness for Abigail, Newton refuses to take her suspicions seriously. She is forced to battle his prejudice before he agrees to join forces with her and track down the killer.