The act of depriving someone of their liberty is one of humankind’s most enduring responses to ‘crime’ through history. What society has sought to achieve over the years by doing so has shifted across the centuries and there is now a variety of purposes: to express disapproval; for the purpose of straight-up punishment through the removal of freedom; to protect the general public; to rehabilitate, perhaps even to forget about those with whom we simply cannot cope. The letters assembled here come from all parts of the world, and from time immemorial: Thomas Cromwell, Mary Queen of Scots, Eamon De Valera, Al Capone, Martin Luther King and many more. These letters not only reveal what it is like to be behind bars, but raise issues that are still of pressing interest for us today – such as the death penalty, miscarriages of justice, redemption and social change.