(The algebraist’s seal). The San Juan de la Peña monastery’s herbalist monk is dying and summons Diego Galaz, the algebra master that has been educated at the monastery. In his death throes, the old monk discloses to Diego that there is a great secret concerning his birth, and gives him the link that binds him to his family: a puzzling ring in which the Aragon bars and the Israelite symbol of immortality -the sacred emblem of the Temple of Jerusalem priestly lineage– are chiselled. Galaz will start a daring adventure that will lead him to the almogaver camps, set in the Pyrenees mountains, to the Besalu Jewish quarter and to Zaragoza, where he gets an awkward omen and meets the woman of his dreams, Isabella Santángel, a gorgeous convert. From Barcelona, Galaz goes East, and remains unaware of the many dangers and dire situations that he will encounter.