The teacher Claude Lemaire was slain after a parents' evening. Sophie Cross is commissioned by chief investigator Gabriel Deville to examine the victim's private life with her colleagues Amina Dequesne and Fred Fontaine. His ex-wife Sandrine, whom he left for his much younger partner Estelle, and his daughter Jade are on the dead. Sophie finds a suspect in parenting because the 54-year-old Lemaire was suspected of having sexually molested a schoolgirl. The investigators also see a motive for the crime in Estelle's parents