The cave of Lascaux may be closed to the public, but five scholars a day are allowed inside, and Nora Barnes has finagled an appointment. True, she may have fudged a bit in her letter to the authorities, but she does teach art history, and she isn t about to miss her chance to see the world s most famous prehistoric paintings. Nora and her high-spirited husband, Toby, are visiting the Dordogne, in the southern French region of the Aquitaine. Aware...