Six Impossible Things by Elizabeth Boyle

Lord Rimswell is a man of honor and absolutes. If he says something is impossible, it is. Yet his life of right and wrong is turned upside down when he finds himself in a compromising situation with the most unyielding, yet maddeningly beautiful, woman in London. If only he had not given in to the irresistible temptation to kiss her. Now he must marry her. Miss Roselie Stratton is the very definition of impossible—headstrong, outspoken and carrying a reticule of secrets that could ruin more than her reputation.

Kissing Brody is hardly the most ruinous thing Roselie has ever done as a secret agent for the Home Office…nor will she let a marriage of convenience stop her from continuing her work. Little does Roselie realize that she has underestimated Brody’s resolve to keep her safe—for he has hopelessly fallen in love with her and is determined to do the impossible by stealing her heart in return.