Gabriel Saint-André, the head of a wealthy family in the South of France, is being blackmailed by an elusive killer. To free himself from this threat, he is forced to reveal to his family the existence of his illegitimate daughter, Esther. Young and beautiful, she falls prey to an obsessed murderer determined to destroy the Saint-André line. At the age of 29, Esther gives up a promising future to protect her family and expose the killer's motives. With the support of Commissaire Antoine Keller, she unravels the psychology of the serial killer, now known as "Zodiaque". The murderer, who is passionate about esotericism and astrology, sends Esther messages accompanied by a drawing of a Zodiac ring. The texts, which foreshadow his crimes, are inspired by the prophecies of Nostradamus. The "Zodiac" chooses its victims according to their astrological sign. The battle between Good and Evil has just begun...