Jane Hudson, a single American woman in her late thirties, visits Venice for the first time. Upon arrival, by train, she is clearly a little overwhelmed by the crowds and bustle which greet her. She is whisked away by water-bus down the Grand Canal to her hotel, photographing everything she sees. On board are the McIlhennys, a middle-aged American couple who are also staying at the Pensione Fioria.

The hotel owner, Signora Fioria, shows Jane to her rooms. Jane meets some other American guests, Eddie, an artist, and his girlfriend Phyl. As evening approaches, everyone, including Signora Fioria, goes out to dinner, leaving Jane alone. She makes the acquaintance of a small boy, a street urchin called Mauro, who makes a living from the tourists, but Jane decides to explore Venice on her own, eventually reaching St. Mark's Square, where she is dazzled by the beauty of her surroundings. She orders a drink at a café and observes the early evening promenade. All around her, people are in couples. The sound of Jane's camera attracts the notice of an Italian man, around her own age, sitting at the table behind her. Jane is embarrassed when she realises he is looking at her, and leaves.

The next day, Jane continues her sight-seeing with Mauro, but later, on her own, she sees a beautiful red glass goblet, in the window of an antique shop by a canal. When she goes into the shop she is disconcerted to see that it is owned by the man who had watched her in the square the previous evening - Renato di Rossi. She buys the goblet and Renato says that he will try to find another for her, although the glasses are very rare 18th century antiques.

Back at the hotel, Jane strikes up a conversation with Phyl, but is left alone again when she goes off with Eddie. Leaving her camera behind, for once, Jane returns to St. Mark's Square. Taking a table, she sees Eddie and Phyl, with their friends, coming towards her. She moves the chairs to make it look as though she is waiting for some-one to join her, but they pass by without seeing her. Renato comes to the café, but when he sees the upturned chair and untouched drink at Jane's table, he moves on before she has a chance to explain that she is really on her own.

The following morning Jane goes sight-seeing again with Mauro. She returns to the antique shop but Renato is not there. Taking a photograph of it she loses her balance and falls into the canal. Renato calls on her, back at the hotel. Jane is immediately suspicious and questions why he has come to see her. He tells her that he finds her attractive, and Jane admits that she is attracted to him. He asks her out and she is about to accept when the McIlhennys come in to the hallway and show off the six goblets of red Venetian glass they have bought, just like Jane's 'antique'. An angry Jane accuses Renato of having duped her, but agrees to meet him that evening, in the Square.

They spend the evening together and Renato buys her a white gardenia. She agrees to see him again the following night. The next day she goes shopping for new clothes, but when, that evening, she discovers that Renato is married with children, she joins Phyl in Harry's Bar, and both women, disappointed with their men, drown their sorrows, for Eddie is having an affair with Signora Fioria. Renato finds Jane and tells her he is separated from his wife. She relents,goes out with him as planned, and they spend the night together, followed by an idyllic day on the island of Murano. But Jane knows that they have no future together, and prepares to leave Venice. Renato reaches the station as her train is leaving - he has brought her a white gardenia.