A duchess in the dark By invitation only series, book 1.

The first novella in Kate McKinley's erotic By Invitation Only series. A DUCHESS IN THE DARK Miss Daphne Hayward is on the hunt for a safe, honorable husband and she has set her sights on the perfect target. She plans a full-scale seduction that will bring him to his knees, and have him begging for her hand in marriage. But when she mistakenly slips into another man's bed, the passions that quickly ignite threaten to send her well-laid plans...