Did Leonardo da Vinci’s Mona Lisa have a twin? A twin portrait, that is? Just over a century ago, an art dealer traveling in England came across, and purchased, a painting in Isleworth, which he claimed then featured the same model as the one immortalized in Mona Lisa, only younger. Was it an earlier work by da Vinci? (The two works are shown here, with da Vinci’s classic Mona Lisa at left.) Finally, the latest advancements in science allow that question to be answered with more evidence than speculation – and that’s the topic of tonight’s Secrets of the Dead. “Are you warm, are you real, Mona Lisa? Or just a cold and lonely, lovely work of art?” Those answers, and more – tonight on The Mona Lisa Mystery. Check local listings.