San Francisco, 1948. Frank Swiver, down-and-out private eye, with a taste for wine and a weakness for women, accepts an invitation from General Thursby to attend a wine tasting aboard the general's private railroad car. Frank, accompanied by his secretary and lover, Vera Peregrino, finds an old flame, the recently widowed, Cicilai O'Callaghan, chef-owner of Chez Cici, among the guests at the tasting. Thursby wants Frank to find the murderer of his friend, the late Rusty O'Callaghan, whose death from a poison mushroom omelet the cops wrote off as accidental. But Thursby takes two slugs through the pump before the tasting has even begun. Locked into the private carriage until they reach their destination, the guests proceed to pull some corks, and tensions rise as they theorize who among them could be the killer. The cops arrest Vera for Thursby's murder, and while she languishes in her cell, Frank's renewed affair with Cici heats up. He spends his nights with Cici and his days questioning the guests from the tasting to find Thursby's killer and spring Vera. But another murder follows, and Frank soon sees that his romance with Cici is poisonous. He realizes he must either change his perceptions or lose both women, and maybe even his life.