A 20-year old young man who has been brought up by a foster mother in the countryside has fallen in love with another foster child in the same "family" and the two have decided to get married. Just after this decision, the young man's real mother contacts him and asks him to come and stay with her and his father (she is a high-ranking Party official). She is against his marriage but her husband is...

The events that take place on a city bus taken daily by workers, students, intellectuals, housewives and schoolchildren are depicted, and the lives of the two conductors, a hard-working young woman and an impatient and lazy man are contrasted.