The Duke's Diamond - Treasure tales, #2

Payton Hartwell, the Earl of Bellmeer, is on a quest to return signet rings to various less-than-noble men whom a dead man had blackmailed. Instead, he walks into his own kidnapping. Separated from his cousin and friend, and finding himself alone with his kidnapper's Scottish stepsister, his travels take on a serious tone. Saving her from Viscount Manning's despicable plans, as well as Payton's possible murder, takes a turn during a costume ball. Tara Scott cannot believe her stepbrother kidnapped a nobleman and tied him up in his country manor's barn.
She saves Payton from the bitter cold and starvation, then is punished by an irate Viscount Manning. When Payton helps her escape, they find themselves on a journey into Scotland that is filled with ruffians, a Highland bull, wild weather, and a sexual awakening that surprises them both. Back in England at a New Year's ball and the second discovery of a huge blue diamond comes to a head when the viscount and his men attack.
It will take Payton, Tara, and all his friends to thwart a man set on vengeance and treasure.