Ruth Rendell’s greatest strengths as a writer of crime fiction have always been her pitiless eye for human foibles and her ability to crawl around inside the mind of any character, from any walk of life. Here she turns her attention to the servants on a short, posh London block called Hexam Place.

June, elderly companion to an equally elderly “princess” with obscure credentials but plenty of money, has many discontents but hangs on in the hope of an ultimate reward. Henry, a handsome young valet and chauffeur, is bedding both his employer’s wife and daughter. Montserrat’s only duty as an au pair in the Still household is getting Mrs. Still’s lover into the house surreptitiously. Rabia, a widowed Muslim nanny, is so deeply attached to her young charge that she sacrifices her chances to have a life and family of her own. These and others who work for the Hexam Place homeowners form the St. Zita Society—named for the patron saint of domestic servants—to address complaints about their working conditions. Their grievances never seem to go further than their pub discussions because their own lives are so thoroughly entwined with those of their employers.

Haunting the fringes of the group is Dex, a gardener who spent time in a mental hospital after trying to murder his mother, suffers from prosopagnosia (he can’t recognize faces) and receives orders from God through his cell phone. Everyone on the street knows Dex’s history and mental state, yet they treat him as just another servant. They’re all either too lazy or too blind to recognize how dangerous he might be—all of them, that is, except the one person who wants to use Dex’s delusions for his own purposes.

In her Inspector Wexford police procedurals, Rendell produces victims promptly and gets on with the investigation, but in her psychological suspense novels she takes her time about building a little world before she shatters it with a sudden shocking act of violence. The first death in The St. Zita Society occurs almost halfway through the book. By then the reader has come to know the players well and probably has in mind a favorite candidate for the role of victim. A debacle in disposing of a body, as grimly hilarious as anything ever seen on “The Sopranos,” is enough to make the wait worthwhile, but much more follows. Along the way, the social structure on Hexam Place falls apart piece by piece from the bottom up, then comes together again in new and surprising configurations.

The St. Zita Society is filled with people so real and closely observed that only one of them is easy to label a villain. With the rest, the reader may swing between disgust and sympathy—or feel both reactions at the same time. Written with Rendell’s customary grace and precision, this is not a novel for readers who want a lot of action and bloodshed, but it will reward those who crave deep character studies and thought-provoking questions of guilt and innocence.

Sandra Parshall, a longtime resident of the Washington area, is the award-winning author of the Rachel Goddard mysteries. The fifth in the series, Bleeding Through, will be published September 4.