The Duke's Deception (Duke #5)
Fenella J. Miller

Unable to stay in a bachelor establishment she moves to Frating Hall, with the permanently impecunious Lord and Lady Grierson. She discovers, to her horror, that Charles, and his younger brother, Edward are involved with the local smugglers.
Theo's dissembling inevitably leads to misunderstandings and heartbreak and with her reputation in tatters Marianne flees to London. But she is ostracised by society and is obliged to find refuge at Drayton House, a small estate in Hertfordshire. Here her life turns into a nightmare.
Can Theo catch his spy, save Edward and Charles from the gallows and rescue the woman he loves before she is lost to him for ever?