Grumpy, rakish military man Caspian Arundel, Duke of Concord, knows the recipe for a perfect Christmas: no mistletoe, no mulled wine, and certainly no revelers. The last thing Caspian wants is for some runaway bride to move into the empty castle where Caspian is training his militia. He especially doesn’t want to live near a runaway bride who constantly chirps about the wonders of the coldest holiday of the year. Miranda didn’t plan to run away from her own wedding. She didn’t even plan to wed. But when her aunt and uncle tell her that they’ve secretly posted the banns on her behalf, she decides to flee. Even if she looks ridiculous running in her loveliest gown down the streets of London looking for a hack, and even if she has nowhere to go except her great-aunt's crumbling castle on the Sussex coast. At least she can finally celebrate Christmas just like her parents always did and create a place for her fellow spinsters and bluestockings to escape their overbearing relatives. Caspian Arundel, Duke of Concord, is furious. Women have taken over the castle that his men were planning to stay at. Worse, they want to celebrate Christmas there. Caspian has no time for Christmas or women. Not when that beastly Bonaparte might attack any day. He has a particular dislike for Miranda, the leader of this despicable group of females. She already ruined his cousin’s wedding, and clearly she has every intention of ruining his militia and ensuring he’ll never be able to return to the front. If only she weren’t so enticing .

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…