Joanne Froggatt's latest role after the close of "Downton Abbey" will be one of stark contrast in the PBS miniseries "Dark Angel."

Instead of the loyal maidservant she played in Abbey, the actress will take on the persona of a real-life serial killer, Mary Anne Cotton.

"People kept saying to me, 'What did I want to do after 'Downton?'' I jokingly kept saying, 'Oh, I don't know something completely different. Play a murderer or something," Froggatt said Tuesday at the Television Critics Association winter press tour.

"Then this script came along and I thought, 'Oh, I better put my money where my mouth is."

Cotton, the first known female serial killer, killed three of her four husbands and 11 of her own children.

"It was lovely, actually, to have something to focus on, to go straight on to because I think I would have felt the weight of the end [of 'Abbey'] so much more if I hadn't had something to focus on straight away so it was fantastic for me," Froggatt said of her new role.