Il sorriso venuto dal passato

An "artistic" mystery awaits Martin Mystère, in the form of a version of Leonardo da Vinci's "Mona Lisa", slightly different from the original, but still equally masterfully executed and, above all, equally ancient. The work tempts an unscrupulous collector who does not hesitate to steal it. To discover the story behind this "impossible" painting, Martin goes to Milan, in search of a solution document... Martin Mystère, Diana and Java are in northern Italy to investigate the origin of a mysterious "Mona Lisa", an apparently twin painting of Leonardo's "Mona Lisa", but which has some strange differences compared to the original. Their search will lead them to a thirteenth-century stronghold that hides an incredible secret...