The film opens with a title card reading: "In Prague, in 1968, there lived a young doctor named Tomas..." We then see Tomas (Daniel Day-Lewis) enter a hospital locker room and tell a nurse to take off her clothes. She protests, saying he'd already seen everything the night before. Nevertheless, he persists and she complies, with a couple of doctors watching through the translucent glass and wondering how he does it.We get another title card introducing us to Sabina as the woman who understood him best. Sabina (Lena Olin) and Tomas have just had sex, and she's holding a bowler hat in her hand as they lie in bed. It's implied that the hat is a bit of a kink for Tomas where she's concerned. Tomas says he has to go, saying he never spends the night at a woman's place. They have sex again and we cut to another title card telling us that one day, Tomas was sent to a spa town to perform an operation. The town is very small, almost village-like, but the spa itself is quite nice by 1968 standards, especially if you like oompah bands. After the operation, Tomas wanders the property, and he gets caught up watching some men play chess on a board floating in the pool when there's a huge splash nearby. It's a woman named Tereza, and when she leaves the pool area after drying off, he follows her out. Tereza works at the bar there, and she doesn't even notice him until she begins her shift. For once he's playing it cool, though, and she's the forward one. When he asks to have his drink order charged to his room, she finds it funny that he's in Room 6, because that's the time that her shift ends. Although he's supposed to be heading back to Prague by then, he decides to wait for her. She joins him on the bench carrying a copy of Anna Karenina. They talk about themselves briefly but eventually he has to leave.But Tereza has gotten into his head, and Sabina has picked up on it, but it's also clear that he's talked about Tereza with her. Tereza shows up at Tomas' apartment one night, saying she's looking for another job and she's in town to see friends. He invites her in and he goes to his usual "take off your clothes" line. Her response is to sneeze, saying she may have caught a cold on the train. He offers to examine her, and during the examination he begins to undo her clothes, but again she becomes the aggressor, kidding him passionately enough that they damage the apartment. They move to his bed and have sex, and when he wakes up the next morning, he's still holding her hand. He slips a copy of Oedipus Rex into her hand before leaving for work.At the hospital, Tomas is confronted by the Chief Surgeon (Donald Moffat) and Jiri (Tomasz Borkowy), who wonder if he's going to be taking a job in Geneva. Tomas says he doesn't want it, and they wonder if he'll be made to go by way of Russian interference. Tomas meets with a patient named Pavel (Pavel Landovský) for a follow-up visit. Afterward, he breaks a date with a nurse and she's angry because she'd heard that someone had moved into his place, and this was the proof she needed.Tomas is still fooling around with Sabina, however, and she's skeptical of the relationship he has with Tereza. He asks her to help Tereza find work as a photographer. She thinks it's for a cynical reason but she agrees to it. The three of them meet later in Sabina's apartment and Tereza is encouraged to reach a little higher with her photography.Tereza has a nightmare. She tells him that she dreamed that he was making love to Sabina and she was forced to watch. He calms her down and talks softly to her to get her back to sleep.We see Tomas and Tereza, along with Jiri and the Chief Surgeon, along with Sabina, out at a club celebrating Tereza's photos getting published. They spot a table nearby composed of Communist Party officials and are discussing whether or not they're scoundrels when one of them goes to the band and tells them to stop playing the pop music they've been playing, and instead play a patriotic Soviet tune, to which the table of Party officials sings along. Meanwhile, Tomas offers up a theory in which he compares the actions of Oedipus to the Russian leadership, noting that Oedipus did the right thing in punishing himself, whereas the Russians did not when they realized what happened when Stalin took power. The Chief Surgeon suggests that he write it up as an essay to be published, but he demurs. The band suddenly shifts back to modern-sounding music and the Russians all leave angrily.Tereza gets up to dance and grabs the first man she sees to dance with her. Later on, as they talk about it, she realizes that he was actually a little jealous about it. The two of them tease each other about it and it turns into a decision to get married, with Pavel and his pet piglet among the witnesses. The officiant's speech about Socialism amuses everyone in the room and he refuses to finish the ceremony. At their celebration later, they adopt a puppy and name her Karenin, after Anna Karenina.Tomas writes up his opinion piece comparing the Soviets to Oedipus. The Czechs are looking to emancipate from the Russians, and the editor thinks this will be a convincing argument. On the way out, Tomas chats up the editor's secretary. Meanwhile, Tereza is swimming in a public pool while a women's exercise class goes on nearby. She begins to imagine the women naked, and Tomas walking among them. Tomas comes home late one evening and Tereza confronts him about the other women, saying he can't hide it from her. He tries to deny it but she gets dressed and starts to leave. The phone rings and when he answers it, he clearly gets a warning. He goes after Tereza and pulls her back to the house, just in time to watch a Russian Army tank go by. It's the Soviet invasion of Czechoslovakia, and we get a mix of newsreel footage and the film together as Tomas joins in protests and Tereza photographs the tanks moving in. Tomas spots Sabina in her car, headed out to Geneva. Tereza slips the film to a foreigner, asking him to get the photos published. She's not done taking photos, though, and one of the last images she captures is a Russian soldier pointing his gun directly at her.We cut to Tereza being confronted by a Russian interrogator (László Szabó) telling her that she could conceivably be shot for giving her pictures to foreigners. The Russians, meantime, have printed the photos from the cameras they confiscated and are using the images to identify dissidents.Tomas and Tereza decide to leave while they can. They pack up their stuff and join the caravan of cars headed out of Czechoslovakia. Their destination is Switzerland.At a political meeting in Geneva attended by Sabina, where someone is talking about this act of political aggression in invading Czechoslovakia, and she challenges him to go back and fight, rather than remain an émigré encouraging others to do so. She leaves the meeting, and another attendee follows her out. He's a local professor named Franz (Derek de Lint), and he challenges her unfocused anger. They go to lunch and continue the discussion, and Sabina opines on how the world is getting uglier. The two of them leave the restaurant and Franz says he has to leave shortly to give a lecture. She decides to travel with him. During the ride, Franz reveals that he's married, but that doesn't matter to Sabina. They begin to kiss passionately in the compartment while the man dozing in there with them pretends he's still asleep.Tomas and Tereza arrive in Geneva and she tries to sell some of her photos of the invasion, but she's told it's not a timely story anymore. However, based on what she's brought in, she might make a good fashion photographer. She doesn't really like the idea, at least not at first.At Sabina's apartment, Franz is watching her create an art piece involving broken mirrors. She puts on the bowler hat and removes her outer jacket, revealing lingerie underneath. Franz offers to take her to Amsterdam, and she protests at first, wondering why he never has sex with her in Geneva. He says something about being inhibited doing something like that in the same city as his wife. Shortly after he leaves, Tomas arrives. It's the first time they've met since he came to Geneva and they spend some time catching up. He starts to leave but she puts the had on again and they engage in some frenzied lovemaking.Sometime later, Sabina calls Tereza and they meet up. Tereza asks Sabina to be her model for nude shots. The two of them meet up at Sabina's apartment and drink a bunch of wine before proceeding with the photo shoot. Afterward, Sabina picks up the camera and tells Tereza to take off her clothes, saying it's her turn. Tereza is shy but begins to comply. Sabina begins photographing her before she's quite ready and it turns into a bit of a game, with Sabina snapping photos of Tereza wearing only underpants as she ducks around the room. It begins to get serious and Sabina begins to pull down the underpants. We cut to later and Tereza is now fully nude and being photographed by Sabina, but they break down laughing. The door opens and it's Franz, wondering what he's interrupted. Franz announces that he's left his wife. She agrees to let him stay in her apartment for a little while, until he gets his bearings. She agrees to let him stay and he leaves, saying he'll be back the next day. Sabina asks Tereza to leave as well. When Franz comes in the next day, the apartment is completely empty except for some broken mirrors. Sabina has decamped to a nearby hotel. We see Sabina in bed with Tomas, and she's musing about where she's going to go from there. Perhaps Paris, or America. She says it's possible that she's seeing him for the last time as well.Tomas comes home later and finds a note from Tereza. She's gone back to Prague and taken the dog with her. As the train pulls in, it's clearly a very different city. Soviet officers take her passport and her camera before she even gets off the train. We see Tomas out and about in Geneva but he's clearly not getting anything out of what he's doing so he finally decides to drive himself back to Czechoslovakia. His passport is collected and his bags examined before he's allowed to proceed. He returns to his old place, where Tereza is clearly surprised and happy to see him.Tomas tries to get his old job back, but the article he'd had published is still hanging over his head. Now, if he's willing to sign a letter denouncing the article, all will be forgiven and he can be a brain surgeon again. He seems willing to sign it, given that it's a confidential document that nobody will see, but changes his mind when he bumps into Jiri, who asks him about it. So instead he's assigned to a clinic, treating one person after another with minor ailments. An official at the Interior Ministry (Daniel Olbrychski) visits him at the clinic and tries to talk him into signing the retraction by pretending he's on Tomas' side. He also presses Tomas for information about the people who published the piece, but Tomas isn't especially helpful and he refuses to sign the letter. As a result he loses his job as a doctor and becomes a window washer.Tereza gets a job in a bar. An underage patron comes in drunk and asks for a drink. She gives him a soft drink instead. Naturally he gets belligerent but she sends him out. Another patron at the bar, a regular, comes up and accuses her of serving minors. She denies it but still another, much larger patron, intervenes and he withdraws from the bar altogether. This new man, whom we know only as "The Engineer," (Stellan Skarsgård) says he came in by chance and he gives her his address.Meanwhile, Tomas is washing windows when the woman in one apartment recognizes him as a doctor and calls him inside. She gives him a glass of wine and says she's suffering from back pain. He tells her "Take off your clothes" and she complies. But as she does so, he notices that there are photos of her alongside various Communist Party officials nearby. This doesn't seem to bother him, however, because when Tereza gets into bed with him that night, she notices that his hair smells like another woman. She notes that he has a way of separating love and sex, but she doesn't have that in her. Sometimes, though, she wishes she could.Shortly thereafter she makes her way to The Engineer's apartment. It's sparse but has lots of books, including Oedipus Rex. He begins to fondle her but she's distracted, thinking that someone else is in the apartment. He demonstrates that nobody's there and goes back to seducing her. She's compliant but rather detached; in fact she braces herself for it. We next see her speaking with a former Ambassador (Erland Josephson), explaining how she was probably set up by the Party, possibly as a blackmail target. She arranges to meet with Tomas in a public place and tells him that she wants to get away, that Prague has gotten ugly. He points out that their passports have been confiscated, but she has an idea.The couple moves to the countryside, living and working on Pavel's farm, alongside Pavel's nephew (Pavel Slabý). Life is idyllic for them until one day they notice that something appears to be wrong with Karenin. It turns out that the dog has cancer. They decide to put the dog down rather than let her suffer. Tomas has the drugs they need to get the job done, and Tereza comforts the dog while she dies.Tomas and Tereza, along with Pavel, his nephew and another farmhand take the farm truck to a tavern several miles away. The nephew dances with Tereza while Tomas watches. Pavel convinces Tomas to spend the night at the tavern with Tereza and take the truck home the next morning. Tomas agrees and this gives him permission to drink that evening.We cut to a beach in California. Sabina has moved to America and is using the seashore as inspiration for an art piece she's working on, when a letter arrives from overseas. The letter is from Pavel, telling her that Tomas and Tereza were killed in an accident on the way back from the tavern.We get a flashback to the tavern. The others have left and Tereza dances with Tomas, then he leads her up to their room. He covers her eyes for the last few steps so that he can reveal that they're in Room 6. The next morning, the truck is making its way back to the farm in the rain. Tereza asks Tomas what he's thinking about, and he says he's thinking about how happy he is. We get a view of the wet road as the film ends.