Marjorie Littlefield - an immensely wealthy, older woman - is haunted by the death of her daughter Mariam many years ago. Marjorie is especially troubled because she suspects her son Chasley may have drowned his sister. Thus, Marjorie plans to leave her fortune to her cat Pluto.
Desperate to ask Mariam what really happened on the day she died Marjorie has fallen under the influence of Brandy and Sherry Westin - a mother-daughter duo who hold seances. During these Sherry supposedly contacts spirits of the dead. To hold these spiritual encounters the Westins run a kind of spa/psychic retreat/business conference center where their rich clients are held almost incommunicado with the outside world.
Enter Sarah Booth and Tinkie, private detectives who are hired to check out the Westins and protect Marjorie from being fleeced. They pose as Marjorie's maids to get into the retreat, and big trouble ensues. People at the retreat die and disappear under suspicious circumstances, and almost everyone there behaves oddly. Plenty for the gals to investigate. Meanwhile, Sarah Booth and Tinkie are under pressure in their private lives because Sarah's fiance (Graf) and Tinkie's husband (Oscar) object to their dangerous line of work.
It's an interesting premise but the book is disappointing. The characters are not well-rounded and not believable, and some of the regulars in the series are hardly present at all. In addition, the story is filled with unlikely plot contrivances: wealthy guests remain at a retreat where people are being murdered left and right; a stiff elderly butler and an obnoxious young cook engage in sado-masochistic sex; Marjorie allows Chasley - who she dislikes and distrusts - to stay in her suite; Graf and Oscar disguise themselves to lend a hand in the investigation, and so on.
One big problem with the story is that the Westins are a shrewd team. They could - in two seconds - google Sarah Booth, Tinkie, Graf, and Oscar to discover they're all imposters. Also the motives for the crimes are murky and the solution is unlikely. Finally, the end of the book strains credulity to breaking point.
One mildly amusing touch is Sarah Booth's personal 'haint'(ghost) Jitty - who shows up periodically impersonating a variety of private detectives from books and movies.
I've read several books in this series that were pretty good, but this isn't one of them.