Duke by Day, Rogue by Night - Nelson's Tea Series, #2

His identity is in jeopardy-and so is his heart. When a number of ill-advised financial dealings threaten her father's reputation, Lady Constance Danbury finds herself facing an arranged marriage to a cruel man nearly twice her age. Willing to do anything to escape the betrothal, she boards a merchantman bound for Spain to enlist her estranged aunt's aid. But when the ship is overtaken by pirates, her dream of freedom disappears as memories of her mother's death at the hand of corsairs flood her with determination never to bow down to a pirate. Percival Avery, Duke of Blendingham, is a member of Nelson's Tea, an elite group of patriots assigned to protect England's shores at any cost.
Service to the Crown requires heroic sacrifice, and for Percy, that means living a double life. On land, he is a mysterious nobleman, and at sea, he is a dangerous pirate infiltrating the underbelly of society. He takes great care to keep his two identities separate, but while investigating a notorious pirate ring, Percy finds them coming to a head. Now, he must choose between completing his mission and saving the life of the beautiful woman he recognizes as his commander's niece.
Returning Constance to London isn't easy, however. She will have none of it, even as her traitorous body longs for the devil who saved her. But she is not the only one struggling for control. Passion has no place in a world of intrigue and espionage, and despite his feelings, Percy swears to protect her-not only from the enemy but from himself.