On their first night in Paris, the Gamaches gather as a family for a bistro dinner with Armand’s godfather, the billionaire Stephen Horowitz. Walking home together after the meal, they watch in horror as Stephen is knocked down and critically injured in what Armand knows is no accident. When a strange key is found in Stephen’s possession, it sends Armand, his wife Reine-Marie, and his former second-in-command at the Sûreté, Jean-Guy Beauvoir, deep into the secrets that Armand’s godfather has kept for decades. A gruesome discovery in Stephen’s Paris apartment makes it clear the secrets are more rancid, the danger far greater and more imminent, than they realized. Soon the whole family is caught up in a web of lies and deceit.