Colin (Rupert Everett) and Mary (Natasha Richardson) are a British couple vacationing in Venice for the second time. They are not married, but Mary has two children, who have been left at home with her mother. We are shown glimpses of a tall man dressed in white, who seems to be observing them from afar. Late one night, they become lost as they search for a restaurant. As they wander around, they meet Robert (Christopher Walken), the British-Italian owner of a local bar. He is the very elegant-looking man in all white. Over several bottles of wine, he tells them stories about his sadistic father, an Italian diplomat. Robert also talks of the cruel tricks his younger sisters played upon him.
After this late evening, Colin and Mary try to walk back to their hotel through the labyrinthine streets of Venice. However, they lose their way and are forced to sleep in the streets. In the morning, hungover and hungry, they make their way to an outdoor restaurant in the square at St Mark’s Basilica. There they see Robert, who realizes his thoughtlessness at not guiding them back to their hotel, and insists they come back to his home and dine there. They discover he and his wife Caroline (Helen Mirren) live in a spacious, Moorish-styled apartment.
The purpose of Colin’s and Mary’s trip is also to revitalize their relationship, and they decide to marry upon their return to England. However, Robert and Caroline are a very mysterious couple who attract and repulse the other pair. Robert is clearly obsessed with his past. Gradually, he draws them further into his influence much as a spider entraps his prey.