His Lordship's Blood - His Lordship's Mysteries, #4

Even after a year of having an earl for a lover, Dominick still isn't prepared for the dazzling high society of Bath with its ruinous gossip and scandalous fashions. All he wants is to uncover who his parents are so he and Alfie can return to their quiet life in Scotland. But as long-buried secrets come to light, Dominick finds himself trapped in a web of intrigue that may prove impossible to escape.
When an old acquaintance winds up dead, it's almost a relief. With a murder to solve, Alfie and Dominick have a distraction from the jaws of fate slowly closing around them. Assuming, of course, that they can avoid being murdered themselves. Alfie knows how much learning the truth about his family means to Dominick, but as events begin to spin out of control, it soon becomes clear that knowledge may come with a terrible cost-their happiness, their relationship, and even their lives.
His Lordship's Blood is the fourth novel in the His Lordship's Mysteries series.