In the cab scene, in chapter 1 of Part III, the novel suggests the beginning of Emma's affair with Léon: the two spend hours inside a hired carriage with the blinds drawn, driving aimlessly around Rouen and its outskirts, and the narrator does not show what happens inside, only what the city sees from outside.
The day before, Léon declares himself to Emma at the inn where she is staying, and she agrees to meet him at the cathedral. That night she writes a letter to cancel the meeting, but she does not know his address and decides to deliver it herself. In the cathedral, Emma kneels in the Virgin's chapel to pray, and the verger who shows them around drags the two of them past tombs and statues. Léon makes his escape with her, "because he had the impression that his love" would evaporate inside there.
At the door, Emma hesitates and says it isn't decent; Léon replies "It's common practice in Paris!" To the coachman, who asks where to, she says "Wherever you like!" The carriage then begins to cross the city, and the residents see "a carriage with its blinds drawn appearing constantly, more closed than a tomb and tossed about like a ship." At midday, an ungloved hand comes through the curtains and throws out scraps of torn paper. At about six o'clock, the carriage stops in a lane in the Beauvoisine district, and a veiled woman gets out without turning her head.
The cab sums up Emma's love: it needs an enclosed space, in motion, with no fixed address. The Thursday routine that follows shows the same pattern on another scale, because Emma does not know how to inhabit a place, only how to pass through it in search of sensation.