On returning to Sunderland, Mary Ann discovers James has had a change of heart about their relationship and says he cannot marry again so soon after his first wife died, as it will unsettle his children. Furious, Mary Ann sets out to get rid of the apparent impediments.

The two-part drama, Dark Angel, from Line of Duty makers World Productions, is based on the extraordinary true story of the Victorian poisoner Mary Ann Cotton. Travelling 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.