PARIS -- The mystery of who killed Admiral Nelson is to be explained in a previously unknown novel by Alexandre Dumas, author of The Three Musketeers, discovered by a French researcher and going on sale in June, the book's publisher said on Tuesday. Le Chevalier de Sainte-Hermine (The knight of Saint-Hermine) is a classic Dumas adventure story about the start of the Napoleonic empire and includes a swashbuckling account of the battle of Trafalgar, according to Jean-Pierre Sicre of Phebus press. "The description of Trafalgar is indescribably brilliant. And in it we learn that it is the hero of the...