Gabriel Allon once served in intelligence, and he had no equal. He retired a long time ago, leads a quiet family life and does not want to remember the past. But the past reminds itself again. A historian who studied the Vatican's secret ties with Nazi Germany dies under mysterious circumstances. Evidence suggests that the crime was committed by a killer nicknamed Leopard. And his next victim, as intelligence finds out, should be one of the most powerful people in the world. It is hard to believe. It's almost impossible to prevent... But Gabriel Allon always knew how to do the impossible!