“Nobody should be allowed to live in a house too big for them,” she continues. “We should have forcible repossessions, redistribution of land and housing to the people who need it.”

Meanwhile, the well-connected, once-rich family at the heart of the mystery, the Chiswells, is as dysfunctional, power-abusing, greedy and backstabbing a group of snobby jerks as you could hope for.

Not only are the Chiswells poor advertisements for the elite classes, but also their upper-crusty names — Izzy, Fizzy and Flopsy, to provide just a sampling — are ridiculous. They’re keen on nicknames. Behind the back of Raphael, one member of the clan, they call him “Rancid.”

With a mystery this big and baggy, it can be hard to keep track of who has done what and why. The questions raised include: Why is Jasper Chiswell, Britain’s culture minister, being blackmailed by Geraint Winn, the husband of the country’s sports minister? (The Winns’ dog is named Gwynn, which is the most alluring thing about them.) Who is more hateful: the repugnant Jasper, his younger, semi-insane wife, or his charming, criminal and resentful son from an earlier relationship? Why is it a good idea to hide your listening devices in a Tampax box? If “Lethal White,” which gives the book its title, is not a noxious new item on the Starbucks menu, then what is it?

Also, will Strike and Robin finally get enough of a grip to dump their significant others, ditch their emotional baggage and realize that they’re meant for each other?

“Lethal White” is an old-fashioned novel, by which I mean that it is 650 pages long and that few of its protagonists’ activities, emotions and motivations are left to the reader’s imagination. The bad traffic that makes it hard to get to places on time; the chronic pain caused by Strike’s prosthetic leg; the constant whither-our-relationship conversations Robin has with her husband, and Strike has with his current and past girlfriends; what the detectives think about those conversations; the painstaking way they go about solving the multiple strands of the Hydra-like mystery — all of this is exhaustively described and occasionally exhausting to hear.