On Assassination of Abraham Lincoln, five days after the end of the American Civil War, John Wilkes Booth and Michael O'Laughlen enter a tavern in Washington, D.C., and approach Thomas Gates to decode a message in Booth's diary. Thomas recognizes the message as using the Playfair cipher and begins to translate it. While he does so, Booth leaves for Ford's Theatre to assassinate President Abraham Lincoln. Thomas solves the puzzle and realizes the men are members of the Knights of the Golden Circle and are Copperhead (politics). A fight breaks out, and Thomas rips several pages from the diary and throws them in the fireplace. Thomas is shot, and the gunman retrieves only a page fragment. (thetvdb.com)