Maximilian Cale, the Duke of Lyons, accepted long ago that his kidnapped brother was dead. When a cryptic note from investigator Tristan Bonnaud claims otherwise, Max seeks out Tristan's sister, Lisette—and is infuriated to learn that Tristan has also mysteriously vanished. Have the siblings perpetrated an elaborate hoax? Or is the fiercely protective beauty as innocent as she claims them to be?

Fearful that the powerful duke will destroy Tristan's career in his zeal for the truth, the clever Lisette convinces Max to accompany her to Paris in a joint search for their loved ones. But their journey takes a seductive twist when they pose as an ordinary husband and wife—not an English duke with a tarnished family name, and the illegitimate daughter of a viscount—and discover an exhilarating passion free from the damning secrets of the past. With the line between danger and desire blurred, they discover that some mysteries, like those of the heart, are answered tenfold in the blissfulness of a true and trusting love.