The spy in petticoats

"For the sake of her country Letty had agreed to undertake a dangerous mission playing the part of her brother Grenville. She had accepted the assistance of the naval architect David Gray, a man she had grown to love. What would she do when she had to don her ruffles and petticoats once more and leave Mr Gray? Before their agonising farewell, fate placed them both in a perilous position, and they had to make their way into enemy France to escape safely once their mission was over."--Publisher description.