Watch Dark Angel Online at Couchtuner. In this chilling 2-part drama, Joanne Froggatt stars as serial killer Mary Ann, a poisoner whose methods leave no visible scars, allowing her tally of victims to mount, unsuspected by a Victorian society unable to conceive of a woman capable of such terrible crimes. Traveling around the North East, she insinuates herself into unsuspecting families, marrying and creating new families of her own – before killing them, taking their money and moving on.