Deadly Climate — Richard Barth

To celebrate winning a sleek new camper in a church lottery, septuagenarian sleuth Margaret Binton invites her friends Berdie, Sid, and Durso to share a winter vacation in warm, beautiful Miami. The Miami they find, however, is a district of dreary nursing homes. And one of those inhospitable establishments is not merely depressing, it's downright sinister.

At Forstman's Rest Home, the residents are eerily silent and passive, and the premises are patrolled by a vicious guard dog. But one of the inmates slips Margaret a note and before they know it, the feisty gang of four is embroiled in a wildly dangerous investigation, stalking an enemy whose vicious cleverness they fail to appreciate--until they come within a heartbeat of disaster.