Joanne Froggatt stars in "Masterpiece: Dark Angel" on May 21

Last Updated by Dale Fisher on

Joanne Froggatt, who stole the hearts of millions of viewers as Anna, the loving and resilient lady’s maid on Downton Abbey, stars in a totally different role in this spine-tingling drama. Dispensing death from the spout of a warm teapot, Froggatt plays the notorious Victorian poisoner Mary Ann Cotton, Britain’s first female serial killer.

Tune in for Masterpiece: Dark Angel on Sunday, May 21 at 8:00 p.m. on Nine PBS.

Dark Angel - Masterpiece Dark Angel: Coming May 21 Watch the true story of Mary Ann Cotton, the infamous Victorian serial killer.