A Tip of the Cap by Rebecca Connolly

With Cap in hand…Malcolm Colerain, Earl of Montgomery, needs a wife. He has four children, a peerage, and a demanding secret occupation as a member of the London League; all of which give him a fulfilling life, so a proper marriage of convenience is all he seeks. But when he meets Elizabeth Owens, things begin to change. Distance becomes difficult, convenience becomes rather inconvenient, and his exciting life as a spy turns on its head.
…Love comes to call…Beth Owens seizes the chance to marry the handsome and striking Earl of Montgomery, marriage of convenience or not. Her heart is his for the taking, and she is determined that he eventually will. But the more she learns about her husband, the more he puzzles her. He has secrets, she is well aware, but just how many and how deeply do they run? And when she finds a few secrets of her own, will they ever have a chance at love?