Jessica Biel stars as Cora, a young wife and mother who suddenly and inexplicably commits a violent crime while at a public beach with her husband and child. Cora does not deny responsibility but claims to have no idea why she did it. Why would this seemingly normal woman commit such a random and senseless act of violence? While the facts of the crime appear to be indisputable, Detective Harry Ambrose (Bill Pullman) suspects that there is more to the case than meets the eye and begins to thoroughly examine Cora’s past in search of an explanation.