Shy spinster Hazel Howard has a secret. She's been exchanging letters to decode French spy communications with someone utterly inappropriate: a man. Fortunately, the handsome, charming Lord Aston has no knowledge of her identity. She would never be brave enough to speak with him at a ball, even if their letters have become flirtatious… Lord Aston is eager to know the female cryptographer who has been assisting the war effort. When she writes she will be in a remote region of Northumberland over Christmas, he seizes upon an excuse to visit. If only he knew precisely who she is. Hazel is startled to find Lord Aston visiting the militia beside the castle where she is holidaying with her spinster friends. When Lord Aston seems under the impression that his secret letter writer is someone else, she's not certain whether to be relieved…