The Opera (S01E07)

After dropping his daughter off for her dance lesson at the Palais Garnier, Raymond Sittler is attacked on the opera's steps. Moments later, he begins to convulse, collapses, and tragically dies. His mistress, initially a suspect, is subsequently murdered at the Barbès-Rochechouart station, also by poisoning. As the investigation unfolds, Jo finds herself drawn to the esteemed Sorbonne University, where she encounters a troubled student and his driven girlfriend, both of whom may hold crucial information.