The first half of the film is set in the year 1959 in Moscow. The plot centers on three young Russian women: Katerina, Lyudmila, and Antonina, who come to the capital city from smaller towns around Soviet Russia. They are placed together in a workers' dormitory room and eventually become friends.Antonina (Raisa Ryazanova) is seeing Nikolai, a reserved but kind young man whose parents have a dacha in the country.Katerina (Vera Alentova) is a serious, upstanding woman who strives to earn her chemistry degree while working at a factory. She is asked to house-sit an apartment for her well-to-do Moscow relatives (a famous professor's family) while they are away on a trip.Lyudmila (Irina Muravyova), a flirty go-getter looking for a well-to-do husband while working at a bakery, convinces her to throw a dinner party at the apartment, and pretend that they are the daughters of Katerina's professor uncle, as a ploy to meet successful Muscovite men. At the party, Lyudmila meets Sergei, a famous hockey player, who falls in love with her and marries her even after discovering the truth about her origin. Katerina meets Rodion (Yuri Vasilyev), a smooth talker who works as a cameraman for a local television station. They start dating.During Antonina and Nikolai's wedding, Lyudmila and Antonina find out that Katerina is pregnant. Upon discovering that Katerina deceived him and is not the daughter of a professor, Rodion refuses to marry her and believes that she is to have an abortion. Katerina is unable to get an abortion because her pregnancy is in a late stage and ends up giving birth.The film shows Katerina, with tears in her eyes, setting her alarm clock in the dormitory room she shares with her daughter, Aleksandra (subsequently played as a grown young woman by Natalya Vavilova).The film then takes a 20-year leap forward in time to present day 1979. Katerina is shown waking up to the sound of an alarm clock in her own apartment. She is still single, but she has gone from being a down on her luck university student to becoming the executive director of a large factory. She has a lover, an older married man named Vladimir (Oleg Tabakov), but she leaves him after he shows himself to be cowardly and disrespectful. Despite her successful career, Katerina is unfulfilled and weighed down by a deep sadness. She is still close friends with Lyudmila and Antonina. By this time Sergei has quit playing hockey and become an alcoholic, having divorced Lyudmila, who is working at a laundry. Antonina is happily married and has three children.One evening, when Katerina is returning home from Antonina's dacha in the countryside on an elektrichka (electric train), she meets a man, named Gosha (Aleksey Batalov), who starts a dialogue with her. She sees his shabby boots and dismisses him at first, but the dialogue continues. Soon afterward they start seeing each other. Gosha is an intelligent tool-and-die maker who believes that a woman must not make more money than her husband, so Katerina doesn't tell him about her position. As their romance begins, Rodion unexpectedly reenters Katerina's life when he is assigned to film an interview with her to do a report on her factory's success at exceeding its production quota. At first, he does not recognize Katerina, but when he does, he wants to meet his daughter. Katerina tells him that she does not want to see him again. Nonetheless, Rodion shows up uninvited at her apartment when Katerina is having dinner with Gosha and Aleksandra. Rodion tells Gosha and Aleksandra about the interview, and Gosha finds out that Katerina is a factory director. His pride is hurt not only because of Katerina's high position and large salary, but also because she has deceived and offended him before, and he leaves the apartment. Unable to stop him, Katerina is upset with Rodion. She reveals to Aleksandra that Rodion is, in fact, her father.Gosha disappears from Katerina's life. She becomes frantic. Lyudmila, Antonina, and Nikolai come to her apartment to comfort her. Nikolai gathers what little information Katerina knows about Gosha and sets out to find him. Gosha has been binge-drinking at home for days, and Nikolai, during a "men's talk" over vodka, defends Katerina and convinces Gosha to return.Sobered up Gosha brings drunk Nikolai to Katerina's flat and asks for a dinner. As he eats, Katerina watches him, saying "I have been looking for you for so long". Gosha replies that it's been only a few days, to which Katerina repeats, with tears in her eyes, "I have been looking for you for so long..."