In October 2007, a striking portrait of a young woman in Renaissance dress made world news headlines. Originally sold nine years before for around $20,000, the portrait is now thought to be an undiscovered masterwork by Leonardo da Vinci worth more than $100 million. How did cutting-edge imaging analysis help tie the portrait to Leonardo? NOVA meets a new breed of experts who are approaching "cold case" art mysteries as if they were crime scenes, determined to discover "who committed the art." And it follows art sleuths as they deploy new techniques to combat the multibillion-dollar criminal market in stolen and fraudulent art.