The whole brigade is under tension after the explosion of an SUV that injured two gendarmes. The SUV was spotted at the scene of a robber's murder. Would the murderer have decided to attack the gendarmes ? Leah is quick to receive a message of claim, the killer promising not to stop there and do justice himself. Paul and Sabine are intrigued by the writing of this email which seems to have been written by a gendarme.

The body of a man disguised as a pirate is found on the beach. Visibly drowned dead, he is bound feet and fists, would he have suffered the torment of the board? And who is this man, would he be a real pirate? Paul and Leah discover that he had received the famous black mark as in the treasure island, someone threatened him ? Is it related to the treasure of Gaspard Dot that the victim claimed to have discovered ?