She had been the chattel of French monarchs. Francois I bought her. Louis XIV set her up in Versailles. Napoleon moved her into his bedroom. She was Italian, created by Leonardo da Vinci over four years labor in Florence, but France was her home and there she stayed for four centuries. Then on Aug. 20, 1911, the space she occupied on the walls of the Louvre was discovered bare. The theft shook France: the country's borders were closed, administrators at the museum were dismissed, enemies of traditional art were suspected of evil intentions. (The avant-garde poet Guillaume Apollinaire was arrested as a suspect; he implicated Pablo Picasso. Both were eventually dropped as possible culprits). As the months went by, the fears grew that the Mona Lisa had been destroyed. Then the Louvre received word from the Uffizi Gallery in Florence. The Italian officials said they had arrested a man named Vincenzo Perugia, who had brought the Mona Lisa to a local antiques dealer in order to sell it and restore it to Italy. (Perugia, who had single-handedly stolen the masterpiece, may or may not have been part of a plot to inflate the prices of forged Mona Lisas; he had lost contact with his co-conspirators and decided to sell the original wood panel painting himself.) On Jan. 4, 1914, the painting was returned to the Louvre. Hailed as a patriot in Italy, Perugia, while found guilty, served only a few months in jail. Patriotism is also a refuge for art thieves.