Dead Man Docking by Mary Daheim

B&B hostess Judith McMonigle Flynn and her closer-than-a-sibling cousin Renie would be crazy to turn down a free, 1930s-themed South Pacific islands cruise aboard the magnificent San Rafael, the pride of the Cruz Cruises fleet. Unfortunately, the fabulous pre-launch party is as far out to sea as the passengers are likely to get, after the body of their VIP host, Magglio Cruz, is discovered stuffed in the piano and the cruise is cancelled.

Suddenly free to gad about San Francisco with their marooned shipmates -- at least one of whom is possibly homicidal -- the cousins decide to join glamorous, martini-quaffing Rick and Rhoda St. George and their wheezy white pooch, Asthma, for a bit of amateur sleuthing. But the route to Magglio's murderer may not be such smooth sailing. And if Judith, Renie, and the St. Georges aren't careful, they may all end up leaving their hearts in San Francisco . . . and the rest of their mortal remains as well!