It's the autumn of 1962 in the idyllic Suffolk village of Melstead St Mary. Evelyn Devereux's husband Kit is planning their 20th wedding anniversary party. But as they prepare to celebrate, Evelyn receives an anonymous letter that threatens to unravel the secrets she's kept hidden for many years - secrets that reach back to the war and her days at Bletchley Park. A sweeping story of family, love and betrayal.