Wednesday late afternoon. Leaving the Palais Garnier, where he had just dropped his daughter to her dance class, Raymond Sittler is assaulted on the steps of the Opera. A few seconds later, before convulsing, he collapses and dies on the porch ... A time suspected his mistress is murdered at Barbès-Rochechouart station poisoned. The investigation leads Jo to the prestigious Sorbonne University and to the door of a troubled student and his ambitious girlfriend.