Marseille 1561. A certain Michel de Nostredame, better known as Nostradamus, saves three shipwrecked individuals and heals them from the plague. In return, he demands that they take an oath: "I save your three lives, give me three others in exchange. Here are three opals; your children will be the others." Seventy years later, in Bordeaux, Walaya du Matray, an adventurer and daughter of an African princess, Erik Gustavson, a Swedish mercenary, and Joachim Pratentis, an officer in the service of Cardinal Richelieu, cross paths. The three have nothing in common, yet their fathers were the ones who once swore the oath. Now they are forced to uncover the secrets that Nostradamus left behind seventy years ago. However, the ambitious Richelieu will do everything to prevent the Ars Magna of the famous Nostradamus from falling into anyone's hands but his own.