Inside Bletchley Park, England's TOP SECRET codebreaking center, Dilly Knox enlists a small team of girls to crack some of the enemy's toughest codes. Whilst Margaret Rock is a trained statistician, the newest recruit is Mavis Lever, 19 years old and a student of German romantic poetry. A friendship develops between this unlikely pair as pressure mounts on them to decipher intercepts which could change the course of the war. But it's not all-night shifts and Enigma machines; there are dances, pranks, and even a touch of romance.