Boston medical examiner Dr. Maura Isles is shocked to discover that the murdered woman looks exactly like her. For Maura, an only child, a DNA test confirms the startling fact: the mysterious doppelganger is in fact her twin sister. Now an already bizarre homicide investigation becomes a disturbing excursion into a past full of dark secrets and twisted truths. It is a journey that leads Maura to the mother she never knew--an icy and cunning woman...

Based on the award-winning novel by Margaret Atwood and inspired by true events, Alias Grace tells the story of Grace Marks (Sarah Gadon), a young, poor Irish immigrant and domestic servant in Upper Canada who - along with stable hand James McDermott (Kerr Logan) - finds herself accused and convicted of the infamous 1843 double murder of her employer Thomas Kinnear (Paul Gross), and his housekeeper Nancy Montgomery (Anna Paquin).