In 1496, a beautiful princess was preparing to marry in Milan. Bianca was the daughter of Duke Ludovico Sforza and betrothed to Galeazzo Sanseverino, commander of the duke's armies. Portraits were often commissioned during the Renaissance to mark major events in a subject's life, and a court artist named Leonardo da Vinci was given the task of memorializing Bianca.

Tragically, the princess died soon after her wedding. Then her portrait, the last evidence of her existence, was also lost.

At a New York City gallery in 2007, Peter Silverman saw a portrait catalogued as "German, early 19th century." Thinking it misattributed and regretting not buying it once before, he scooped it up for a mere $19,000 and began a long quest to discover its origins. He hardly dared utter the "L" word: Leonardo.

Giants in the field of art history and scholarship soon would, though, as the best of connoisseurship was used to authenticate La Bella Principessa. Science would then confirm their judgments. The picture was carbon-dated, digitally examined with multispectral imaging, even scrutinized for fingerprints--and one of Leonardo's was found along with a palm print. Bianca was identified as the subject, and her clothes and hair were matched to those of her period.

Many in the art community still would not believe, but Silverman persisted and, with the help of Leonardo scholar Martin Kemp, discovered its provenance: the tribute book from which the picture had been removed. After more than 500 years the beautiful princess was home again.

The picture is valued at $150 million, but its value to the art world is incalculable--and its story is unforgettable.