In a church in Douai, a body is found staged in a manner reminiscent of the great Inquisition trials of the region in the 15th century. Commander Clara Baudran is forced to team up with Lieutenant Jérôme Santerre, her childhood sweetheart. She thought he had become a priest, but 20 years later she finds him working as a cop and father to a teenager. Once she gets over the shock, she has no choice but to rely on him to help her solve this mysterious murder... even as investigators are faced with a new victim.

Marion and Camille, 15, are inseparable. They arrive on a southern island for their final school trip, full of excitement and expectation. It’s a time of firsts, and the abrupt end of carefree days.