When Rosie Frost was jilted on her wedding day, she didn't think life could get any worse. But six years later in the throes of the Second World War, she is unceremoniously dismissed from her job after they discover her illegitimate child. Thankfully, top secret war office Bletchley Park recognises Rosie's talent and recruits her to decipher their Italian naval signals. Proud to be doing her bit for the war effort, Rosie settles into her new life. But when she spots a familiar face at the Park, Rosie's world threatens to come crashing down once more. Can she put the past behind her in order to excel at the job she was born to do? And will her hard work help safeguard her nation's future...?