Fact-based story about a serial killer, who marries multiple times, only to kill her husbands, & the children she had with them, so that she can claim the insurances on her dead mates. Joanna Froggatt of 'Downton Abbey' fame, stars as Mary Ann Mowbray, who poisons everyone who gets in her way of her goals. Her final mistake comes when she murders her step-son. Finally she is caught. She is arrested, tried and convicted of this one murder. She is sentenced to death by hanging.