July 2006, the city of Aix-en-Provence is under particular strain. The trial of Mathias Rousseau, the man who called himself the "Zodiac," is about to begin. Called back to France to testify, Esther Delaître moves in with Quentin, the child she adopted, at her brother Jérôme's house on the shores of Lake Geneva in Switzerland. But the disappearance of little Lucie Daguerre throws everything into question. The family of the missing child runs the Daguerre Institute, a renowned school where Mathias had stayed for a few months when he was younger. Is the "Zodiac" pulling the strings from his prison cell? Is he the victim of an imitator? This new case takes Esther back two years...