mary ann cottonGolden Globe winner Joanne Froggatt will go from playing kind-hearted, if often unfortunate, Anna Bates to portraying real-life Victorian age serial killer Mary Ann Cotton. In her first post-Downton Abbey gig, Froggatt will begin shooting Dark Angel in August for ITV. The two-part drama is produced by Line Of Duty‘s World Productions and is based on the true story of Cotton, who used adultery, bigamy, fraud and murder to “better” herself socially and financially before being convicted and hanged for her crimes in 1873.

Inspired by the book, Mary Ann Cotton: Britain’s First Female Serial Killer by David Wilson, the drama will see Cotton, an apparently loving wife and mother, newly-returned to her native North East of England. But faced with abject poverty and an ailing husband, the ruthlessly determined woman sets out to pursue her own desires in order to achieve a better life. Using arsenic as her weapon of choice, Cotton travels around the North East insinuating herself into unsuspecting families, marrying and creating new families of her own and then killing them and absconding with their money. The real Cotton killed as many as 21 people including three husbands.

Dark Angel is written by Gwyneth Hughes (The Girl) and will be directed by Downton‘s Emmy and BAFTA award-winner Brian Percival. Producer is Jake Lushington (The Bletchley Circle) and exec producers are Kirstie Macdonald (The Fear) and Simon Heath (Line Of Duty, Code Of A Killer) for World Productions. Endemol Shine International is selling world rights.

Downton Abbey‘s 6th and final season finishes shooting this summer. Froggatt’s recent work off of the Grantham estate has included James McAvoy-starrer Filth. She’s also eyeing feature drama Starfish, a star vehicle she would also produce and which is in development.