A painting that is not only a masterful work of art but also a fascinating footnote to an old mystery goes on display this week in Richmond's Virginia Museum of Fine Arts. It is Peter Paul Rubens' 10|½-in.-by-15-in. oil sketch for his Pallas and Arachne. The finished painting is long lost, and presumably destroyedbut still to be seen in a copy made three centuries ago by the Spanish painter Velàsquez.
One day in 1656, Diego Rodriguez de Silva y Velàsquez, court painter to Spain's proud Philip IV, was finishing a portrait of the King's daughter, the blonde, five-year-old Infanta Margarita. Around...