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

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

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.