An amateur caver emerges traumatised from a labyrinth of subterranean grottos where he says he lost his friend. Laurene tries to unravel fact from fiction in his witness statement before contemplating a perilous descent. At the same time, Cora thinks that the Mayor's daughter has been kidnapped by a mysterious group of activists who are leaving their marks on the walls of Villefranche.

A traditional ritual of a school with mortals, which is producing tension in the city. Cora has visions of an underground network.

A Sabine barless shootout causes a hunt for a band of armed criminals. Cora and Romano spy on trucks that enter the forest each night.

A wife of a hero commits suicide locally. Laurelyne is sure that he is not what he appears to be and investigates on his own.

Siriani questions Bertrand about the disappearance of Marion. Nounours and Camille investigated the death of a man who knew the events of all his neighbors.

The truth about Marion finally comes to the surface. Bertrand gets violent. Lauren and Cora are caught in a dangerous plot.