Mourning his brother's recent death, Pierrick accepts his best friend Tessa's invitation to stay in her family home — at last, a week alone. But when her gets there, he finds the house already occupied by Tessa's sister Marie.

A police captain specialized in Crime History is investigating on the discovery of a corpse found on the beach of Saint-Malo. She tries to convince her temporary teammate that their case would be linked to piracy.

In Brittany, a notary is killed with shots to the head. His wife Joséphine is a suspect. Her husband had just sold part of their property to two shady real estate developers who wanted to transform the little fishing village into an ultra-modern marina for wealthy clients.