Mary Ann Cotton finds a desperate way out in this scene from Dark Angel, premiering Sunday, May 21, 2017 at 9/8c on MASTERPIECE on PBS.

Starring Downton Abbey’s Joanne Froggatt, Dark Angel tells the story of Mary Ann Cotton: loving wife, mother, and serial murderer. See it Sunday, May 21, 2017 at 9/8c on MASTERPIECE on PBS. #DarkAngelPBS

Joanne Froggatt explores the frightening true story of Mary Ann Cotton, Britain’s first female serial killer. Dark Angel airs Sunday, May 21st, 2017 at 9/8c on MASTERPIECE on PBS.

Actress Joanne Froggatt explores the painful past and nuanced character of real-life serial killer Mary Ann Cotton from Dark Angel, as seen on MASTERPIECE on PBS.

Joanne Froggatt explores what Downton Abbey’s Anna Bates would think of Dark Angel’s Mary Ann Cotton. Dark Angel premieres Sunday, May 21st, 2017 at 9/8c on MASTERPIECE on PBS.

Joanne Froggatt (Downton Abbey) portrays the mother, wife, and infamous Victorian serial killer Mary Ann Cotton in Dark Angel, a one-night television event coming to MASTERPIECE Sunday, May 21, 2017 at 9/8c on PBS. #DarkAngelPBS

See what’s coming to MASTERPIECE in 2017, including: Home Fires, an encore presentation of Wolf Hall, Dark Angel, and My Mother and Other Strangers.