Two Brides and a Duke by Tessa Candle

He is back from the grave and hiding someone in a cave. Why would the duke’s daughter trust such a knave?
As if returning from the dead were not taxing enough, Delville, the missing rogue heir to the Duchy of Pallensley, discovers that he is still most inopportunely engaged to a silk-sashed demoness. If he resurfaces to become a duke, she will expect her presumed dead fiancé to make good on the betrothal, and Delville would rather poke out his own eye. But he has another reason for not letting his true identity slip: he is a spy trying to discreetly rescue an abducted child from a dangerous criminal.
Things would be a lot less complicated if Lady Eleanor stopped popping up wherever she had the least business being. It is almost as though she is following him—which she probably is. He does have that effect on women. Mistaking her for a lady of the evening and kissing her does not appear to have helped matters. Yet he can hardly be blamed. It was rather dark in that cellar, after all.
Eleanor, scathingly sarcastic daughter to the Duke of Grendleridge, has a problem, and his name is Lord Auchdun. The insinuating pest follows her everywhere and cannot seem to comprehend her refusing his offer of marriage, by which he means to remove the taint of her mother’s scandalous past. Eleanor would sooner die an old maid than marry such a moralizing bacon-brain.
But evading Auchdun keeps throwing her into the company of a mysterious man who looks like a labourer, but sounds like a gentlemen—though he certainly does not act like one. When she discovers he is hiding a prisoner on her friend’s property, Eleanor has a choice: tell the Marquess of Fenimore of this skullduggery, or assist an insufferably presumptuous and probably dangerous rake in his crimes. And the kiss is of no consideration at all in the matter. Not in the least.