This novel is based on a fact—that of a crime so incredible that it caused amazement equal to the horror it inspired; the public sentiment aroused by this atrocity went far to provoke the sudden French Revolution of 1848. The author is responsible for everything in the novel save this central fact, and for the details of the life of the period, which are largely taken from contemporary newspapers.

Charles Laure Hugues Thobald, duc de Choiseul-Praslin (29 June 1804-24 August 1847) was a French nobleman and politician, who served as a member of the Chamber of Deputies in 1838-1842. Choiseul-Praslin's suicide, occurring while he faced trial for the murder of his wife, Fanny Sbastiani, caused a scandal which in turn contributed to the outbreak of the 1848 Revolution and the fall of the July Monarchy. In previous years, the Choiseul-Praslin household had been the scene of violent confrontations between the duke and his wife. Among others, Fanny de Choiseul-Praslin accused her husband of hiring a governess, Henriette Deluzy-Desportes (or Henriette de Lucy, Henriette de Luzy), in order to estrange her from her children. Deluzy-Desportes, whom she had fired six weeks before being killed but had not left the household, was also alleged by Fanny to have been the duke's mistress (with whom, she suspected, the duke planned to elope).The duchess repeatedly threatened to separate from her husband.—