Leonardo da Vinci’s irreverent young apprentice delights in mischief and defying the aristocracy in this historical fiction middle grade novel from E.L. Konigsburg, the Newbery Medal–winning author of From the Mixed-Up Files of Mrs. Basil E. Frankweiler.The mystery of the “Mona Lisa!” Why did Leonardo da Vinci, the greatest artist of his time, devote three years on a painting of the second wife of an unimportant merchant when all the nobles of Europe were begging for a portrait by him? And why did he put up with an apprentice who was a liar and a thief? No one knows for sure. But this story of Leonardo, his wayward apprentice Salai, and the Duke of Milan’s plain young wife, Beatrice d’Este, may hold the clue to the most famous—and puzzling—painting of all time.