And Then There Was One by Michele Castleman

Six weeks after Lyla Smith dragged her sister’s dead body onto the Lake Erie shore, she escapes her small Ohio town to work as a nanny for distant relatives on their remote private island. Plagued by strange memories and drowning in the guilt she tried to leave behind, Lyla struggles to break up with her boyfriend and forget her feelings for her sister’s girlfriend. Especially now that she has met another girl on the island who seems to be flirting with her.

Lyla’s first family dinner is a tense affair, and mid-argument the matriarch, Crystal Payne, takes a sip from her wineglass and dies. Suddenly everyone is a suspect. From rival interests in Crystal’s corporation to family secrets that won’t stay hidden, there are too many people with a motive for murder, and Lyla’s trapped with an unknown killer.

The only way to save herself is to be free of the secrets that drag her down. But when the killer strikes again, it’s only a matter of time before Lyla drowns.