In 1849, Dickens wrote to the Times expressing his dismay at the callous and bloodthirsty crowd crammed into the Bermondsey streets for a public hanging. Frederick and Maria Manning had been found guilty of murdering Patrick O’Connor. It might have been nothing more than a few paragraphs in the law columns had detectives not been involved in an exciting hunt for the couple using the latest technology, the electric telegraph; had Mrs. Manning not been a Swiss lady’s maid in a Duchess's household; and had the couple not been in an uneasy ménage à trois with the victim.

Even if Maria Manning was not the murderer as her husband claimed, she was legally culpable. She pointed to the danger of welcoming foreigners into the home. Uneasiness nowadays would include relations of power...