A whodunit set in the art world. The protagonist is Julia, an art restoration expert in Madrid who is cleaning a 15th Century painting. The painting shows a duke and his knight playing chess and the story begins when, with the aid of x-rays, Julia discovers an inscription hidden in a corner, ´Who killed the knight?´ Autor: Arturo Pérez-Reverte Fecha: 1999 ISBN: 9788420427843 ISBN 10: 8420427845.