The murder of prosecutor Adrien Jacquart at the Riviera hotel exposes the explosive secrets of the Pontavice-Caron family: Blanche, his married lover, is arrested; Eugénie, his ex-fiancée, has a son who could be Adrien's; and Giulia, the housekeeper, is hiding a compromising debt. Commissioner Raven leads the investigation, aided by Léonie, who remains determined to prove her father's innocence. But Raoul Delaunay, a shady businessman, seems to be manipulating events behind the scenes. A final twist, however, turns everything upside down and reignites the mystery: who is Jacquart's murderer?

The murder of Edgar Girault plunges the Riviera even further into chaos. Giulia, suspected by Raven, is narrowly saved by Joseph Neuville, the charming son of the newly arrived hotel owner. But Raoul Delaunay continues to blackmail her to obtain a compromising notebook. Meanwhile, Marthe Pontavice-Caron testifies against her working-class son-in-law. She believes Jean Berthier had a motive: he had just learned that Louis was not his biological son. Blanche is released. But tensions rise at the town dance, where Eugénie sees her husband taken away by the police. For Léonie, the evening turns into a nightmare.