Actress Joanne Froggatt explores the story of serial killer Mary Ann Cotton.

Mary Ann Cotton, the subject of ITV's new historical drama Dark Angel, was a Victorian Sunday school teacher, a nurse, a wife and a mother.

Fans of Downton Abbey’s Anna Bates were likely spooked by Joanne Froggatt’s character in Dark Angel: the manipulative real-life serial killer Mary Ann Cotton.

Dark Angel stars Downton Abbey alum Joanne Froggatt as one of the most notorious women in British history: the nation’s first female serial killer, Mary Ann Cotton.

In her first post-Downton Abbey gig, Joanne Froggat will begin shooting serial killer tale 'Dark Angel' for ITV in August.

The jump from Anna to Mary Ann was a big one, especially considering that Froggatt started work on Dark Angel just two days after wrapping the final season of Downton Abbey.

See Mary Ann Cotton's letters she wrote from her Durham prison cell As ITV drama Dark Angel comes to its conclusion tonight, read what the real-life killer wrote about in her final days ...

ITV's creepy AF drama Dark Angel is based on the true story of one of the UK's most prolific serial killers, Mary Ann Cotton. A serial killer who stands out not only for her heinous acts but for ...

ITV has nicknamed Mary Ann Cotton “the Dark Angel”, and her story has been told with Joanne Froggatt playing the one-time nurse who poisoned 21 of her husbands, lovers, children, stepsons and ...

Joanne Frogatt as Mary Ann Cotton and and Laura Morgan as Maggie Cotton in the first episode of Dark Angel(Image: ©JustinSleePhotography2015) ...