Céline, supported by Alex, discovers that Philippin was developing a high-performance concrete. Enough to crush the competition: solid, durable, and 10 times less polluting than the others on the market. A discovery that would be worth billions.

Celine and Alex confront Damien; Celine's mother arrives with new secrets; Leopold makes disturbing confessions about his family's past.

The room in which a discovery of a person named Philippin was found was rented by a woman named Esther Smith.

Céline assaults William and Jacques removes her from the investigation; Daphne continues the work; Chamfort, with financial support from QMG, was providing Philippin with the means to carry out research in the lab.

Céline comes up against resistance from Simon and McNeil, who are rather stingy with information; Alex pushes Johnny against a wall.

Céline and Daphne discover that Esther was an engineer specialising in large structures. With a committee of experts, Esther was in charge of evaluating the options for the construction of a third link between Quebec City and its southern shore.

Celine and Alex uncover the identity of a man; a new corpse is discovered; Celine figures out who the killer is.

In the small town of Fermont, Celine and Alexandre must solve the murder of a woman who was found inside the city's "wall," wearing a Chinese mask.

At Chateau Frontenac, a body cemented in a bath launches Céline on a new investigation.

The body of Father Sebastian, ruler of the Abbey, is found riddled with crossbow arrows; Céline and Alex inspect the crime scene which is located in the cave of Frère Jacques very close to the place where Véronique was killed.

The details surrounding the autopsy of Esther's body reveals that she was thrown overboard from the ferry.

Celine is now interested in looking into the murder of young Gregoire three years prior, as the two deaths are linked by method, among other things.

Celine believes that multiple murders are connected, while Jacques refuses to admit there's a serial killer and doesn't send reinforcements.

Céline wants to reopen the investigation into the murder of her cousin, Véronique Jolicoeur; Alex continues his investigation into the death of Marie-Thérèse at the abbey.

Alex believes the abbot's killer wanted to send a message; Martin finds clues; Céline studies the file of the investigation into Véronique's murder and makes disturbing discoveries about Damien.

More and more suspects appear for Philippin's murder. The first suspicions fall on Prévost, who was found in a coma after attempting suicide; the attraction between Alex and Joanie is inevitable.