On August 21, 1911, a handyman named Vincenzo Peruggia, who had helped build the Louvre’s protective glass cases, tucked the Mona Lisa under his work smock and walked out. The museum had more than 400 rooms and few guards, and staff took a full day to notice, assuming the photographers had it. According to the famous account, the theft was ordered by Eduardo de Valfierno, an Argentine con man who styled himself a marquis and did not want the painting at all. What he wanted was the headline.

This episode lays out the scheme credited to him: six forgeries painted by restorer Yves Chaudron, shipped to six wealthy and unscrupulous buyers before the theft, then each sold as the stolen original once the news broke. It follows Peruggia, left for two years with a painting he could not sell, to his arrest in Florence in 1913. And it weighs the evidence that the whole story was invented by journalist Karl Decker, whose 1932 article in the Saturday Evening Post is its only source.

• The forgeries were sent abroad before the theft so that customs would pass them as ordinary replicas, with no stolen masterpiece yet to look for.
• Faking a Leonardo meant sourcing centuries-old wood panels, mixing period pigments, and baking and freezing the paint to produce the fine cracking of age.
• The buyers could never complain to the police, since doing so meant admitting they had tried to buy stolen cultural heritage.
• Peruggia insisted he acted alone out of patriotism. He hid the painting in a trunk before offering it to a Florentine dealer who called the police.
• Decker wrote that the Mona Lisa was on canvas and got its size and weight wrong, and none of the six copies has ever surfaced.