Murder at Beechwood / Alyssa Maxwell.

Enhanced descriptions from Syndetics:

For fans of HBO's The Gilded Age , explore the dark side of the alluring world of America's 19th century elite in this gripping series of riveting mysteries...

For Newport, Rhode Island's high society, the summer of 1896 brings lawn parties, sailboat races...and murder.

Having turned down the proposal of Derrick Andrews, Emma Cross has no imminent plans for matrimony--let alone motherhood. But when she discovers an infant left on her doorstep, she naturally takes the child into her care. Using her influence as a cousin to the Vanderbilts and a society page reporter for the Newport Observer , Emma launches a discreet search for the baby's mother.

One of her first stops is a lawn party at Mrs. Caroline Astor's Beechwood estate. But an idyllic summer's day is soon clouded by tragedy. During a sailboat race, textile magnate Virgil Monroe falls overboard. There are prompt accusations of foul play--and even Derrick Andrews falls under suspicion. Deepening the intrigue, a telltale slip of lace may link the abandoned child to the drowned man. But as Emma navigates dark undercurrents of scandalous indiscretions and violent passions, she'll need to watch her step to ensure that no one lowers the boom on her...