A look at the world of codes includes a history of how they have affected the world, from the World Wars to the death of Mary, Queen of Scots, and also looks at what the future holds for the field of cryptography.

The cipher of Mary Queen of Scots --Le chiffre indechiffrable -- The mechanisation of secrecy -- Cracking the Enigma -- The language barrier -- Alice and Bob go public -- Pretty good privacy -- A quantum leap into the future.