When Thomas, Baron Armitage, finds himself on the verge of the Season and suddenly impoverished by his unscrupulous man of business, he has no choice but to make a devil's bargain with his nearest neighbor. In exchange for the funds he requires to reclaim what is rightfully his, he must take his neighbor's intolerable spinster daughter to London for the Season and find the impossible woman a husband.

Miss Mercy Fletcher has got her own reasons to be in London, and they do not involve husband-hunting. She has been fast friends with Thomas' sisters for years, but Thomas has never had the least patience for her and her myriad eccentricities, and Mercy has never had much patience of her own for Thomas' stern severity. In such close quarters, it seems an impossibility that they will make it through the Season without killing one another.

Familiarity is meant to breed contempt, but instead it breeds a new understanding between old enemies. As the Season progresses, friendship turns unexpectedly toward passion. But can their blossoming romance survive Mercy's secrets?