In the August 6th issue of the magazine, Mark Singer writes about Kip Litton, a dentist from Michigan who may not be as fast a marathoner as he says he is. Here Mark Singer and David Grann, who wrote about the French impostor Frederic Bourdin, in 2008, discuss the art of writing about mysterious characters. Also, The New Yorker's fiction editor, Deborah Treisman, explains how and why the magazine is publishing a previously unpublished story by F. Scott Fitzgerald.