Lydia Hetherington is uninterested in society balls or marriage, until her brother's friend, Lord Marcus Sheldon, rides into her life to unseat her from her horse and unsettle her heart. An undercover spy for the government, Sheldon is equally unsettled by Lydia. Complicated by a French spy, her best friend's unrequited love for Lydia's brother, James, and a traitorous villain, Lydia gradually finds her emotions stirred by Lord Sheldon. But what is his relationship with the beautiful Lady Smythe and his part in an old scandal? Lydia faces danger before all deception is uncovered and love claims its reward.