Brazen in Blue by Rachael Miles

Lady Emmeline Hartley has overcome every obstacle life has thrown her way. A spinster, disappointed in love, Em is on the brink of a marriage of convenience, when the man who rejected her heart reappears in need of her help. It gives Em a chance to escape, put to use one her most unusual talents—and perhaps convince him once and for all to risk his heart . . .

Adam Montclair–one of the most successful agents at the Home Office–rubs elbows with the highest levels of society. Even so, he wasn’t to the manor born. No matter how much he desires Em, as a match he is completely unsuitable. While it pains him to be near her, it’s a punishment he richly deserves. Now on a mission to uncover a plot against the government, Adam knows Em’s uncanny ability to recall voices will be essential. Yet as the two thwart the dangers in their path, it may become impossible to deny that Em is essential to happiness itself . . .