My Lady Notorious by Jo Beverley

Desperate to help her widowed sister and baby escape a deadly pursuer, Lady Chastity Ware dresses as a highwayman and captures the first coach to travel down the road. Coming face-to-face with its occupant, the arrogant aristocrat, Cyn Malloren, she orders him to drive her to a remote cottage.

Little does Chastity realize that after long months of recovering from his war wounds, the handsome Cyn is looking for adventure, and being abducted by a cocky highwayman—obviously a lovely woman in disguise—is even more than he had hoped for. Willingly he is drawn into her devilishly reckless plan…and helplessly he is seduced by her wonderfully wicked ways.