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.