Based on the award winning novel by Margaret Atwood, Alias Grace is inspired by the true story of Grace Marks (Sarah Gadon), a poor, young Irish immigrant, who along with James McDermott (Kerr Logan), was convicted of the brutal murders of Thomas Kinnear (Paul Gross) and Nancy Montgomery (Anna Paquin) in 1843. James was hanged and Grace was sentenced to life imprisonment. Grace became one of the most enigmatic and notorious women of her time for her supposed role in the sensational double murder of her employer and his housekeeper, and was eventually exonerated after 30 years in jail. Her conviction was controversial, and sparked much debate about whether Marks was actually involved in the murder, or merely an unwitting accessory.

The novel and the screen adaptation introduce a fictional young doctor, Simon Jordan (Edward Holcroft), who researches the case and begins to fall in love with the fascinating Grace. Although ostensibly conducting research into criminal behavior, Simon becomes obsessed with Grace as he seeks to reconcile his perception of the mild mannered woman he sees with the savage murder of which she has been convicted.