1940: In south-west Ireland, the young and beautiful Lady Charlotte Rathmore is pronounced dead after she mysteriously disappears by the lake of Blackwater Hall. In London, on the brink of the Blitz, Nancy Rathmore is grieving Charlotte's death when a letter arrives containing a secret that she is sworn to keep - one that will change her life for ever. 2019: Decades later, Ellie Fitzgerald is forced to leave Dublin disgraced and heartbroken. Abandoning journalism, she returns to rural Kerry to weather out the storm. But, when she discovers a faded letter, tucked inside the pages of an old book, she finds herself drawn in by a long-buried secret. And as Ellie begins to unravel the mystery, it becomes clear that the letter might hold the key to more than just Charlotte's disappearance. Moving between 1940, 1958 and 2019, this is an unforgettable and spellbinding story of secrets, war, love and sacrifice.