On a crystal clear Mediterranean day, Briony McAllister sits playing with her four-year-old daughter, Katie, while she waits for her mother, Valerie, to join them. Valerie has recently moved to a picturesque town in southern Spain to finally leave behind her turbulent past and find a peace that has always eluded her. Briony has no idea that in a few moments' time her relationship with her mother will change irrevocably. As Katie plays, Briony pulls from her bag an old photo album, found in a box in her mother's new home. As she begins to study the faded photos, a letter falls to the ground. It is addressed to her. My Darling Briony, it begins. As Briony reads the words with mounting shock, realisation dawns. Her mother lied to her about what happened with her beloved grandmother Tessa all those years ago - and denied Briony that most precious of relationships, the type of relationship Valerie now enjoys with Katie. The lives of three generations of women are set to change forever as the past is revisited and the truth unfolds through the undelivered letters Tessa wrote to Briony over the years.