Freelance journalist Margaret Barlow (Murder on the Chesapeake, etc.), in California for a hot-air ballooning vacation, agrees to write a magazine piece on a Napa Valley winery--and is soon ensconced in L'Abbaye Ste. Denise, jointly owned by brothers John and Bryant, plus John's ex-wife Hester and his adopted daughter Lureen. The winery, in deep financial trouble after a yearlong series of accidents/sabotage, could be sold, but only if all the partners agree to it--which, of course, they don't. Then Hester is ground to bits in the grape-crusher; the p.r. woman drowns in a fermenting tank; and the death last fall of a migrant worker may be connected to the winery's current problems. Plucky Margaret enlists the aid of a local newspaper editor, and the two eventually unmask a Swiss pretending to be a Frenchman, as well as unearth a few secret love affairs, before wrapping up the case. Amateurish writing, a dull heroine, and a slap-dash rendering of winemaking--all make for a less-than-memorable third outing for Osborn's fiftysomething sleuth.