In 1515, Leonardo da Vinci built a mechanical lion to entertain King Francis I of France and his guests. Until now, no one knows what happened to this amazing clockwork creation. Over half a century later, when a ten year old boy discovers the lion in a royal storeroom, young Chev doesn't know he will soon embark on a strange and dangerous mission. His quest will lead him many leagues through a French countryside devastated by religious war in search of Leonardo's greatest secrets of all, hidden mysteries that could affect the future of all humanity.