On a sunny summer afternoon by the lake, Cora Bender stabs a man to death. Why? What would cause this quiet, kind young mother to stab a complete stranger in the throat over and over again, in full view of her family and friends? For the local police, it's an open-and-shut case. Cora quickly confesses and there's no shortage of witnesses, but those questions remain unanswered. Haunted by the case, the police commissioner refuses to close the file and begins his own maverick investigation. So begins the slow unraveling of Cora's past, a harrowing descent into a woman's private hell.