What could possibly go wrong on a June cruise in Portugal aboard the Pleasure Boat of Love on the River of Gold? Just about everything if you are St. Paul newspaper reporter Warren ?Mitch? Mitchell and photographer Alan ?Al? Jeffrey, and you're cruising aboard the FelicityAmour on the Douro River. Mitch's mother has won a free cruise for two with Felicity Cruises, Ltd., and the two-person party of Mom and Mitch has expanded to six, with the addition of Mitch's wife; Mitch's best buddy and working companion, Al, and his wife; and Mitch's mother's comfort creature, a curiosity-motivated cat named Sherlock Holmes. Also aboard the ship are a famous European TV personality, Lady T, and her Tuscany vacation home neighbors, Harold and Estelle Koerner. The cruise becomes less pleasurable when Estelle announces that the huge emerald that she wore on the first night aboard has been stolen and Harold accuses Lady T of the crime. The FelicityAmour is confined in port while the theft is investigated, and the situation goes from critical to calamity when a small-time jeweler, who is enthralled by a gigantic diamond worn by Lady T, is found dead of arsenic consumption the morning after dining with the famous Lady. Again, Harold points to Lady T as the perpetrator. With the ship stranded at dockside by a plodding police investigator, the itinerary for Mitch and Al shifts to seeking the whereabouts of the emerald and the identity of the killer. After questioning both Lady T and Harold, Mitch finds himself about to disappear, as if by magic, in the dark of night on the River of Gold.