England – 1865...Colin Layton, Viscount Evanston, is the spy, 'Fox', who must ferret out a double-agent working with the Prussians searching for a ledger, containing the names of British operatives, which has gone missing. Colin must also determine who is writing 'love letters' to him. Are the letters taunts suggesting that someone knows he is a spy or were they truly written by a secret admirer?