The body of Maude Gaillard, 52, a well-liked psychologist, is found dead in the grounds of a luxury hotel. Suspicion quickly falls on Ida Malapeyre, an unstable patient under judicial supervision whose connection to the victim may be more complex than it appears... As Cassandre's team investigates this lead, the investigation takes an unexpected turn: Cassandre is kidnapped! To save her and uncover the truth, the team must unravel a past that some were willing to kill to erase.