Spenser Dumarque, the fourth Duke of Morland, has the entire ton gossipping about his custom to show up at society balls at the strike of midnight, dance one set with a lucky young woman, escort her to dinner, and then leave. Every eligible young debutante wants to be the next lucky lady he selects, but so far none seems to have caught his eye.
Lady Amelia D'Orsay is old enough to be considered pretty much on the shelf by polite society, so she tries to stay away from gossip, and is certainly not interested in fighting the other young ladies for the "Duke of Midnight"'s attention. When she finds out from her scapegrace younger brother Jack that he now owes the Duke 400 pounds, and that this debt means that the family cottage (where Amelia spends every summer) will have to be let, she decides to confront the Duke, and persuade him to forgive Jack's debt. Spenser is flummoxed at being directly approached by the opinionated lady, and has no choice but to dance his customary midnight dance with her, to avoid losing face in public.
What no one in society knows, is that his midnight ritual has nothing to do with finding a suitable bride, but to control his massive fear of crowds, and to stave off anxiety attacks. By arriving precisely at midnight and making a brief public appearance, Spenser fulfils his social obligations, but can leave before the crowds become to overwhelming, and no one's the wiser. Dancing with the pushy Amelia, he's suddenly overcome with a panic attack, and as she refuses to be abandoned on the dance floor, he has to drag her with him out onto the balcony. She realises that something is not quite right, but before she can enquire further, Spenser is approached by two acquaintances, Rhys St. Maur (the Earl of Ashworth and a war hero - also the hero of the second book in the trilogy) and Julian Bellamy (rake, dandy, scoundrel and hero of the third book), announcing that Leo Chatwick, the founder of the exclusive gentleman's club in which all three are members has been murdered, and they need to break the bad news to his twin sister. Amelia insists on coming along, as Lily is an old friend of hers.
At the end of the night, having had a rather bad time of it, Amelia is shocked when Spenser proposes marriage to her in order to save her from any ton gossip (he did after all, drag her from a crowded ball room and disappear with her for most of the night). Even though the thought of becoming a wealthy Duchess is appealing to her, it's only after Spenser convinces her with some pretty head-turning kisses that he's genuinely attracted to her, that she accepts.
A few days after their first dance, Amelia is married to a man who is mostly a stranger to her. It doesn't make it easier that Julian Bellamy crashes their wedding to accuse Spenser of having murdered Leo Chatwick. While drawn to her husband, she makes him promise to prove his innocence before they consummate the marriage. Spenser promises reluctantly, and as he's more and more sure that his decision to marry Amelia impulsively was a good one, sets out to seduce his wife good and proper.
The romance in One Dance with a Duke
is delightful, and while Spenser can seem domineering and aloof and frequently seems to say exactly the wrong and insulting thing in any situation, there are good explanations as to why he's like that. The gradual way in which Spenser and Amelia get to know each other and fall in love with each other is great. Unfortunately, however, there are two other subplots running throughout the book, both of which get seemingly forgotten about for huge stretches at a time, only to be reintroduced just as the main romance plot is getting really good.
First there is the murder investigation, where Spenser, St. Maur and Bellamy try to figure out who killed their friend (this plot is not resolved until Three Nights with a Scoundrel), and then there is the subplot of Amelia's wastrel brother Jack, who keeps getting himself further into debt and expecting Amelia to bail him out. Every time he showed up, I just wanted to scream and put the book away, and Amelia's refusal to see what a complete leech he was made me want to slap her. Apart from that, Amelia's a really nice character. I suspect the Jack subplot was supposed to show how kind and loving and all about family Amelia was, loyal to a fault to her brother, even when he kept disappointing her. Instead, it just made her look like an idiotic sap, and I absolutely sided with Spenser in all their arguments. The subplots also make the structure of the book a lot more loose and meandering, and detracted from my enjoyment of it. So in conclusion, a good book, but less focused on the main romance than I would have liked.