Her Wicked Highland Spy by Erin Rye

As a spy in His Majesty’s Service, Ethan Brodie possesses an unrivaled ability to charm himself out of any situation, and under many a petticoat. Upon his mentor’s death, he retires from the service and promises to settle down to the business of finding a wife. Having lived his life on the edge of danger, he soon loses interest in dancing and grows bored with the season’s debutantes. After all, with three younger brothers to insure the Clan Brodie line of succession, he feels no pressure to marry and, instead, seeks out the dangers and risks of hot-air balloons.

To help out a friend, Ethan agrees to escort his mentor’s widow and her niece, Rosalyn Beaumont, on a seaside holiday. After all, he owes his life to the man many times over. But the more time he spends with Rosalyn, the more her prying ways capture his attention.
Rosalyn Beaumont’s heart broke the previous season when she caught her fiancé in bed with another woman. The engagement ended then and there, but her desire for justice did not. Instead of jumping back into the marriage mart, she sets herself up as a Lady’s Defense, providing services to the season’s debutantes by spying on their behalf.

She prefers to call herself a discreet observer of men’s habits, particularly those relating to manners, hygiene, and, of course, fidelity. She also seeks to answer any personal curiosities a prospective bride might have.

The day comes when she is contracted to observe Ethan Brodie, but as she investigates the man, she finds her professional detachment crumbling as her attraction to him grows. .