The Year is 1792. The French Revolution rages in Paris, the French monarchy abolished, and William Pitt is about to declare war on the Revolutionary government. But all London Society can talk about is the enigmatic highwayman known as the Black Unicorn. 

Newly widowed Elina has no time for highwaymen or politics. Freed from her brutal seven-year-marriage, she is fiercely protective of two things: her new freedom, and her two sisters. But when Elina's family is mistakenly stopped by the Black Unicorn on their way up to the North Yorkshire Moors, and her sister is savagely attacked by one of his men, revenge consumes Elina. For the sake of her sister, she will destroy the Black Unicorn.

And the shooting party at Scarcliffe Towers seems the perfect place to ensnare the mysterious figure.

Another guest at the party, Ashby Harcourt, is known to London Society as the beautiful Portuguese libertine. Elina knows him simply as the whoring companion of her late husband. But this dark Northumberland lord is a man with secrets: a secret love for Elina Brinkley, the daughter of the lofty Marquess of Hertford, and a secret life as the Black Unicorn. But as Elina unravels the mystery surrounding the man behind the mask, she discovers that the Black Unicorn is so much more than just a highwayman.