The series begins with the discovery of Pine, a missing 13-year-old girl whose body is discovered in the shaft-head of an abandoned mine. Cardinal follows detectives John Cardinal (Billy Campbell, The Killing) and Lise Delorme (Karine Vanasse, Revenge) as they attempt to uncover the mystery of what happened to Katie. But as the case grows in scope and horror, a dark secret from Cardinal's history threatens to derail the investigation. Cardinal struggles to right past wrongs that could derail his investigation and end his career, as the case grows more violent and twisted and the clock ticks down on the killer's next victim.