Dinner Most Deadly. John Pickett Mysteries, #4

When Julia, Lady Fieldhurst returns from her sojourn in Scotland restless and out of sorts, her friend Emily, Lady Dunnington decides what Julia needs is a lover. Lady Dunnington plans a dinner party with carefully selected male guests from whom Julia may choose a paramour. Emily also invites a potential lover for herself: Sir Reginald Montague, a man whose urbane manner and dangerous good looks hide a host of unsavory secrets.
Alas, Emily's little dinner is a disaster from the outset. Every gentleman at the table bears some unspoken grudge against Sir Reginald, and then dinner is interrupted by Emily's estranged husband. He and Emily have a heated discussion that ends with Lord Dunnington's vowing to put a stop to his wife's pursuit of Sir Reginald "no matter what it takes." But the coup de grâce comes at the end of the evening, when Sir Reginald is shot dead.
Bow Street Runner John Pickett is summoned to Emily's house, where he is taken aback to find Julia. For in addition to investigating the case, he is faced with the awkward task of informing her that their masquerade as a married couple in Scotland has resulted in their being legally wed. Beset by distractions-not least the humiliating annulment process and the flattering attentions of Lady Dunnington's pretty young housemaid-Pickett must find the killer of a man whom everyone has reason to want dead.