On Halloween night, two couples meet at one of their houses for drinks and hors d'oeuvres before planning on heading out to a massive party.  Dressed in their finest costumes (witch, cowboy, doctor, and Queen Elizabeth I), the hostess brings out a bottle of blue wine she picked up in Peru.  Based on an old Inca recipe, the wine supposedly has truth-telling properties and is brewed from the skins of blue dart tree frogs.  Three of the four drink the wine and the conversation begins to take odd turns.  Some of the "truths" are harmless enough, but progressively get darker and more disturbing.  It gradually becomes clear that the marriage of one of the couples is disintegrating due to a lack of truthfulness, and the other marriage is only held together by lies.