Henry Grave is a senior investigator for the Association of Cruising Vessel Operators. A World War II P.O.W., Henry is as cunning as he is charming, and at 84 years of age, he fits right in with his fellow passengers. The cruising yacht Vesper is anchored off the Greek island of Thera, in the caldera of an ancient volcano, as Henry comes onboard. An Egyptian federal agent was onboard to guard a valuable Minoan cup, but the agent was murdered and the cup, stolen. With the help of a Nicaraguan soap opera star, a New Age spiritualist, and a blind pickpocket, Henry draws on skills honed in a Nazi prison camp to track down a killer who might have his own reasons for taking this particular cruise, reasons unrelated to the sumptuous meals, delightful shipboard activities, and exciting ports of call.