A Body in the Ballroom by Beatrice Marlowe

London, 1891. The newly widowed Marchioness of Merritt is determined to return to society before her mourning period is officially over, despite her mother-in-law's disapproval. Her first event since Edmund's death is a glittering ball at the home of a notorious rake. But beneath the refreshment table, Eleanor finds a body—and a scandal that threatens to ruin the entire Season. With Scotland Yard baffled and the suspects all too polite to confess, Eleanor must navigate a minefield of blackmail, secret debts, and social hypocrisy to solve the crime. She never asked to be a detective, but as she discovers, the only way to survive the Season is to outwit the people who think she's just a woman in a mourning bonnet.