National Treasure - The Book of Secrets (2007)

Several days after the end of the Civil War, two sworn members of the Knights of the Golden Circle (KGC) one of them who happens to be John Wilkes Booth, enter a tavern and approach the great Thomas Gates to decode a message. 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 still loyal to the Confederacy which means that they are traitors to the country. A fight breaks out, and Thomas rips several pages from the diary to keep them from finding the treasure and throws them in the fireplace. Thomas is shot, and the traitorous gunman retrieves a page fragment. Over 140 years later, Ben Gates is telling his great-great-grandfather's story at a Civilian Heroes conference. A Black market antiquities dealer, Mitch Wilkinson, shows one of the missing pages of John Wilkes Booth's diary, with Thomas Gates' name written on it, implicating that Thomas was not only a conspirator, but the grand master of the Lincoln assassination. Ben sets out to prove the innocence of Thomas once and for all.