The Last Supper is considered one of the highest points in the entire history of Western art. Completed by Leonardo da Vinci in 1497, it depicts the reaction of Christ&8217;s Disciples to his declaration that a traitor lay hidden among their number. The portrait, however, conceals much more. In his bestselling investigative novel, The Secret Supper, Javier Sierra explores some of the enigmas presented by the mural that Leonardo da Vinci was, in fact, one of the last of the Cathar heretics. In the following article, Sierra presents the groundbreaking research that led to the writing of his prizewinning novel. It all happened in a heartbeat. The morning of the 13th to the 14th of August, 1943, an aerial flotilla of forty-seven Anglo-American bombers dropped twenty-two tons of incendiary bombs on Milan... One of the bombs fell right on Magenta Street, beside the brick façade of the convent of Santa Maria delle Grazie. After the conflagration the south wall of the church collapsed taking with it the walls of the two lateral chapels from the XVth century. Immediately afterwards, another incendiary bomb hit the sacristy,destroying the oldest parts of the convent, including the area surrounding the refectory and its most precious treasure: an 8.8 meters by 4.6 meters mural on which, in 1497, Leonardo da Vinci had completedhis largest work,the Last Supper. From their air raid shelters, the friars of the convent feared the worst. Nevertheless, against all expectations, the wall of the Leonardo stood intact.