Retired FBI senior investigator Charlotte Diamond is cajoled into taking a Christmas market Rhine river cruise with her partner, glamorous retired queen of the movie screen Brenda Brandon/Boynton. When Brenda invites Charlotte's doctor brother, Chance Diamond, and his minister wife, Marilyn, to join in the trip, Charlotte knows this will be no restful vacation. The "curse of Chance," the travels of whom have always been accompanied by a death or three, does indeed embroil Charlotte and her three travel companions in a complex mix of "inconvenient" robberies and suspicious deaths against a backdrop of quaint German towns, Christmas markets, and Rhine castles. The misadventure of the Rhine river cruise involves an international crime money-laundering Swiss banker and his Italian TV star wife; a "Jack Sprat" pair of elderly spinsters; a doll-fetish Japanese couple; a diamond-dripping, once-kidnapped heiress; a gay novelist and boyfriend; a catatonic mustard dynasty heiress; and assorted other unsavory characters. As the scenically chugs north from Nürnberg to Amsterdam over Christmas week, Charlotte and Brenda track their bet on whether the "curse of Chance" will meet its quota of mayhem, while Charlotte sinks deeper and deeper into what becomes a working vacation. The fourth book in the Charlotte Diamond mystery series.