University of Montpellier. A teacher, Nathalie Josserand, 45, was found dead in an amphitheatre. First suspect for Elli: David Crosnier, 35, assistant teacher, in whose home is found the murder weapon. Nathalie's ex-companion, he has a romantic relationship with one of his students... who is none other than Maryam, Elli's sister! The relationship between Elli and Maryam (who defends David against all odds) is damaged, especially since Elli announces to her sisters that she will be forced to sell their family home... While Elise focuses on David, Clément sees another suspect, Stéphane Rocques, president of the university. He seems to have a secret that he wants to preserve at all costs.