813 Maurice Leblanc - The fourth book in the Arsène Lupin series. When one of Arséne Lupin's victims is found dead in a way that implicates him, he insists on heading the police search for the real murderer. The mystery involves finding a package of letters once written to Bismarck, locating a clock on which the number 813 has significance, as well as causing a reigning emperor to make several journeys incognito.