A lady's guide to etiquette and murder / Dianne Freeman.

Enhanced descriptions from Syndetics:

Frances Wynn, the American-born Countess of Harleigh, enjoys more freedom as a widow than she did as a wife. After an obligatory year spent mourning her philandering husband, Reggie, she puts aside her drab black gowns, leaving the countryside and her money-grubbing in-laws behind. With her young daughter in tow, Frances rents a home in Belgravia and prepares to welcome her sister, Lily, arriving from New York-for her first London season.

No sooner has Frances begun her new life than the ghosts of her old one make an unwelcome appearance. The Metropolitan police receive an anonymous letter implicating Frances in her husband's death. Frances assures Inspector Delaney of her innocence, but she's also keen to keep him from learning the scandalous circumstances of Reggie's demise. As fate would have it, her dashing new neighbor, George Hazelton, is one of only two other people aware of the full story.

While busy with social engagements on Lily's behalf, and worrying if Reggie really was murdered, Frances learns of mysterious burglaries plaguing London's elite. The investigation brings death to her doorstep, and Frances rallies her wits, a circle of gossips, and the ever-chivalrous Mr. Hazelton to uncover the truth. A killer is in their midst, perhaps even among her sister's suitors. And Frances must unmask the villain before Lily's season-and their lives-come to a most unseemly end . . .