Cal Hodges, chief investigator for a Chicago law firm, and his attorney wife, Merle, must find a stolen diamond-encrusted 15th century stickpin, which has already caused one murder and may cause several more unless the thief is captured. On anything but a vacation, Cal and Merle know the murderer is one of their fellow passengers on a river cruise to Prague, but which one? They also know the priceless stickpin is hidden on board, but where? Also endangered...