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

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

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.

Nathan knows Sylvie and the Prévost family well; Daphne discovers that to avoid being removed from the case, Céline has withheld information from her linking William to Esther Smith.

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

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.

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, 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.

Back in her native village, Céline discovers a skeleton in her uncle's orchard; Alex is in charge of the investigation that is causing a stir in the Applegrove community.

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.

Céline discovers that Véronique had a confessor at the abbey; Alex learns that in the 1950s, the monks sold the orchard to Marie-Thérèse Jolicoeur for a pittance.

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.

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.

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

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

Celine and Alex grow closer to the killer; the Jolicoeurs suspect a family member; everyone's certainties are collapsing.