At the age of 71 Bierce crossed into Mexico to join Pancho Villa's revolutionaries. In a letter to his neice Lora, Bierce wrote: "Goodbye. If you hear of my being stood up against a Mexican stone wall and shot to rags please know that I think that a pretty good way to depart this life. It beats old age, disease, or falling down the cellar stars. To be a gringo in Mexico -- ah, that is euthanasia. " Just before he entered war-torn Mexico he again wrote Lora, "I shall not be here long enough to hear from you, and don't know where I shall be next. Guess it doesn't matter much. Adios, Ambrose."

His final letter was dated Dec. 26, 1913, postmarked Chihuahua. In it, he said he expected to leave the next day, partly by rail, for Ojinaga, where Villa was poised to attack a cornered federal army.

It was the last ever heard from Ambrose Bierce. His disappearance sparked investigations, wild speculation, but no answers. The novel The Old Gringo by Carlos Fuentes is a fictionalized treatment of Bierce's disappearance. Glenn Willeford has written a fascinating account of Bierce's presumed death in Mexico. Go to Ojinaga.

James Lienert, who theorized Bierce was executed and buried in the graveyard of the dusty Mexican town of Sierra Mojada in 1914, installed a marker to memorialize the great writer in 2004. The idea's intriguing -- but there are questions. NOTE: Lienert, a Roman Catholic priest, died on January 4, 2010.