A pair of interwoven stories, set in the present and past, that follows Ellie Haworth, an ambitious journalist who discovers a trove of secret love letters from 1965 and becomes determined to solve the mystery of the forbidden affair at their center. As she uncovers the story behind Jennifer Stirling, the wife of a wealthy industrialist, and Anthony O'Hare, the financial journalist assigned to cover him, a love story of Ellie's own begins to unfold with the assistance of an earnest and endearing archivist who helps her track down more letters.