The launch of the latest sparkling wine by Midsomer Vinae Winery falls flat when critic Nadia Simons gives it a scathing review, then guests sampling the vintage start to collapse. Owner William Carnarvon suspects the Farmers' Wives Association of trying to destroy his business, while his wife Diana frets over her mother Matilda, one of the victims. Pathologist Kate reveals the drink was laced with slug poison, but how is the attack connected to the death of a child in a hit-and-run? Barnaby and Nelson are called in to investigate.