The air is thick with excitement and anxiety as Surete du Quebec agents gather in the conference room for the Monday morning meeting of the homicide department. This will be Armand Gamache's first day back since his demotion from head of the entire force, to head of homicide. Complicating matters, he'll be sharing the duties with his former second-in-command, Jean-Guy Beauvoir. Amid blistering social media attacks, Gamache sets out on his first assignment - to find a missing woman. The search for Vivienne Godin is played out against a backdrop of catastrophic spring flooding. Three Pines itself is threatened, as the Riviere Bella Bella breaks its banks. A province-wide emergency is declared and desperate efforts are underway to save towns and cities, dams and bridges. As Gamache leads the search for Vivienne, he develops a profound empathy for her distraught father. With a daughter of his own, he finds himself haunted by the question, how would you feel, if. As the rivers rise, and the social media onslaught becomes crueler, a body is discovered. And the victim's father contemplates a murder of his own. And the question facing both Gamache and Beauvoir shifts. What would you do, if... your child's killer might walk free?