In 1890, when Alex Randall returns from university to his ancestral home of Shillington Hall, he finds his father remarried, less than a year after his mother's death. Dismay turns to anger when a son, Oliver, is born. Convinced the new Lady Randall means to steal his inheritance, Alex flees to London, where he meets and befriends Henri de Saint Clair, a charming, but enigmatic Frenchman. When Alex's friend Charles becomes involved in an illegal duel, and both parties are killed, Alex finds himself on the run from the law, and obliged to leave England. In Paris, he renews his friendship with the still strangely elusive Henri. After a series of misadventures that lead him to the very depths of Parisian society, Henri rescues Alex and restores him to health by means of a mysterious 'restorative', but before long Alex's determination to discover the truth about his friend plunges him into a world darker - and more addictive - than anything he could have imagined.