While swimming in a lake in the Eastern Townships, Kate McDougall makes the macabre discovery of the corpse of a nine-year-old girl. Strong-headed, this former SQ major crimes investigator, fired for insubordination, is first suspected. But when other victims of the same age are found, the Machiavellian work of a serial killer, dubbed by the media the "Monster of the Lake", is confirmed. The one demoted to the region to deal with petty crimes is now catapulted into the most difficult investigation of her career. Plunged into this downward spiral, Kate unleashes her demons, alcohol and sex, and will have to face her painful past to unmask the culprit. The series is an adaptation of the successful novel Le Cri du cerf by Johanne Seymour.