London, 1941. Keen to do her bit in the war, Connie Allinson joins the WRNS and is posted as a letter censor. Her task: to read and alter correspondence to ensure no sensitive information crosses enemy lines. At first, she is not sure she's up to it, but is soon drawn in by the letters she reads, and their secrets. . . Doncaster, 1967. Bored of her domestic life, Connie desperately wants a job, but her controlling husband Arthur won't hear of it. Looking for an escape and plagued by memories of letters she read during the war, she makes a bid for freedom and starts secretly tracking down their authors. Will uncovering their past give Connie the key to her present? And will she be able to find them all before Arthur discovers what she is keeping from him?
