High Water by Lynn S. Hightower
The Smallwoods are a middle-class, small-town, South Carolina family. You would not look for treachery in a family like the Smallwoods. You would not look for bloodstains or double bolt the door. And you would be wrong. The Smallwood siblings gather at their dying mother's bedside. Shocked to discover someone has tampered with her medication. And Georgie Smallwood begins to think the unthinkable - there may be a killer in the family, a killer with a familiar face, old regrets, and unfinished business just to hand. And so begins a lethal dance of musical chairs that will keep the Smallwoods scrambling to see who, if any, are left standing.