During a tourist bus excursion, Rosalba, a housewife from Pescara, is annoyed to find she's been left behind in a roadside cafeteria. Instead of waiting for her husband and children to come back for her, she decides to go home alone. She ends up in a car headed for Venice, a city she is unfamiliar with. The next day is Sunday... and her adventure begins. What should have been a day off turns into a "small vacation" — as she herself puts it in a letter to her family. Her husband, Mimmo, is furious. When he learns that one of his employees, a hydraulics expert, is big on pulp thrillers, he despatches him to Venice to find his wife. In the meantime, Rosalba has begun a new life. She finds work with an old anarchist florist, lives at Fernando's, a somewhat naive Icelander who works as a waiter, and becomes close friends with her neighbor Grazia, an esthetician and masseuse. At Fernando's insistence, Rosalba goes back to her old passion, the accordion. When Costantino, the (hydraulics) detective, finally picks up her trail after many adventures, he also finds himself mixed up in something he hadn't foreseen...