At dawn, in a muddy field of a dairy farm, a woman and a man lie on the ground, murdered. The one who was to prepare a surprise party in the Laurentians found herself, despite herself, the victim of this tragedy. Constance Forest, chief investigator for the Mascouche regional office, maintains that there is another victim in the area, a certain Nancy Lebeau-Pratt. Antoine Chevrier-Marseau and his superior, Fred Bérubé, both investigators for major crimes in Montreal, come to help Constance and his colleague Jonas.