“Downton Abbey” star Joanne Froggatt is to play a serial killer in Victorian-era drama “Dark Angel,” which has been commissioned by U.K. broadcaster ITV.

The two-part show, which is produced by “Line of Duty” makers World Productions, is based on the true story of Mary Ann Cotton, played by Froggatt. The show starts with Mary Ann portrayed as a loving wife and mother, newly returned to her native North East of England. But faced with abject poverty and an ailing husband, we see how ruthlessly determined she is to pursue her desires — and a better life.

Mary Ann turns into a serial killer — a poisoner whose methods leave no visible scars, allowing her tally of victims to mount unsuspected by a Victorian society unable to conceive of a woman capable of such terrible crimes. Travelling around the North East, she insinuates herself into unsuspecting families, marrying and creating new families of her own — before killing them, taking their money and moving on.

Through adultery, bigamy, fraud and murder, Mary Ann betters herself socially and financially. But the more she kills, the greater the risk her crimes will finally be exposed.

The drama is inspired by the book “Mary Ann Cotton: Britain’s First Female Serial Killer” by David Wilson. It is written by Gwyneth Hughes (“The Girl,” “Five Days”), and will be directed by Brian Percival (“Downton Abbey”). The drama is produced by Jake Lushington (“The Bletchley Circle,” “The Devil’s Whore”), and executive produced by Kirstie Macdonald (“The Fear”) and Simon Heath (“Line of Duty,” “Code of a Killer”) for World Productions.

Further casting will be announced before filming begins in August.

ITV’s director of drama Steve November and controller of drama Victoria Fea commissioned “Dark Angel,” which Fea described as “an extraordinary and chilling true story.” The show is supported by Screen Yorkshire’s Yorkshire Content Fund. International distribution will be handled by Endemol Shine Intl.