The Sinner follows a young mother who, when overcome by an inexplicable fit of rage, commits a startling act of violence and to her horror has no idea why. The event launches an inverted and utterly surprising crime thriller whose driving force is not the "who" or the "what" -- but the "why" -- as an investigator finds himself obsessed with uncovering the woman's buried motive. Together they travel a harrowing journey into the depths of her psyche and the violent secrets hidden in her past.