The film begins with a family. In which there are 4 people. The head of the household whose name is Ki-Taek has his wife Choong-sook, daughter Ki-Jung and son Ki-Woo. They are living in extreme poverty. They even have to use someone else’s Wi-Fi. They live in a basement and work hard to survive. They all work folding pizza boxes to support their household. Ki-Woo used to watch various videos on the internet about how to maximize their speed and shows these videos to his family. They all try to make a pizza box as quickly as possible. They are not properly trained and due to this, the pizza boxes are not packed properly. When the pizza shop owner comes to pick up the pizza boxes, she tells them that they did not fold the pizza boxes properly, due to which she will deduct their money. Ki-Woo tells him that he knows that their main worker has left the job they got a huge order. The girl asks Ki-Woo how he knew about their worker. His sister tells them that she knows the worker and he has told them about the order. Ki-Woo tells the girl that she can deduct the money for improper pizza boxes and in return, she can hire him as her main worker. They are all sitting at home eating snacks. A drunkard starts throwing up at their window. Ki-Woo’s friend Min comes to their house. He has a very heavy box in his hand. He puts the box on the table and says that his grandfather has sent it for stoning. His grandfather is fond of collecting precious and rare stones. Min says that this stone is believed to bring happiness to whoever has this stone. Both Ki-Woo and Min go outside. Min tells him that he tutors English to a girl from a rich family and he likes her. Now he has to go to another country for education. He purposed that Ki-Woo should teach her English. Ki-Woo’s English is better than Min’s. He had passed many English tests. Min says that by doing this, his financial condition will also improve. Ki-Woo says he is not in college and has no credentials. Min says that he will recommend Ki-Woo to replace him in this house. He should make a fake degree with the help of his sister. Ki-Jung is artistic and makes a degree for Ki-Woo. After getting ready the next day, Cross leaves for home. While leaving Ki-Woo’s mother asks his father if he should wish him luck as he was going for a new job. He tells his father that of course, although now he has fake credentials, one day he will go to this college.
Ki-Woo reaches the house and presses the bill. The door opens for him. He goes inside and is surprised to see such a big house and a perfect lawn. This house is very big and beautiful. The maid of the house comes to pick him up at the door. Ki-Woo appreciates the house. Maid Moon Gwang tells that the house was built by a very famous architect, after which the new family bought the house from him. She asks him to sit inside and goes and tells Yeon-Kyo about Ki-Woo. There are 4 people in this family. Mr. Park Dong, his wife Yeon-Kyo, a son Da Song and a daughter Da Hyo. Ki-Woo has to teach English to Da-Hye. Yeon-Kyo looks at Ki-Woo’s credentials and sits in the class herself on the first day. Ki-Woo gives a demo class. After the class, Da-Hye’s mother is satisfied with his method of teaching and hires him as an English teacher. Yeon-Kyo is talking with Ki-Woo and her Da-song comes to the lounge. He is a naughty child who plays at home all day. Yeon-Kyo says that Da-song loves painting but his painting teacher has left because of his naughty behavior. Ki-Woo immediately gets an idea and tells Yeon-Kyo that his cousin’s friend is a famous painter and tells her name is Jessica. She has studied at Illinois State. He can talk with her to teach Da-song. When he goes home, he tells his plan to his family. The next day, Ki-Woo introduces his sister Ki-Jung to Da-song’s mother by pretending to be Jessica. His sister acts like a professional teacher. She doesn’t even let Da-song’s mother sit in class on the first day. Ki-Woo goes to teach Da-Hye. Da-Hye says that there is nothing special about her brother, he is just pretending to be special. She adds that she thinks Jessica is Ki-Woo’s girlfriend. Ki-Woo laughs and says, of course, Jessica is beautiful but she is not his girlfriend. Both of them come close in talking and they kiss each other. Yeon-Kyo is worried about Da-song. Maid asks for her juice and she came up with an idea. She tells her maid to take juices for Da-song. By this, she can go into the room and check what was going on, but before she can leave, Da-song and Ki-Jung come out and are sitting in the lounge. Ki-Jung tells Yeon-Kyo that she has looked carefully at Da-song’s paintings and it looks like something bad happened to him. The marks of which are still imprinted on his mind. Hearing this, Da-song’s mother begins to cry but does not tell Ki-Jung. Mr. Park also comes home from the office. He ordered his driver Yoon to drop Ki-jung home. Driver Yoon tries to talk and get close to Ki-Jung on the way. Ki- Jung asked Yoon to drop her off at the metro but Yoon tries to convince her that he can drop her at home. Ki-Jung immediately comes up with a plan and takes off her panties and puts them under the car seat. The next day, Park finds the panties in the car. He comes home and showed panties to her wife. He says that his driver has crossed the limits and asks his wife to fire the driver. The next day, Yeon-Kyo asks Ki-Jung about the night, but Ki-Jung says that she got off at the metro station. Yeon-Kyo is satisfied to hear this and fires the driver. According to her idea, Ki-Jung tells them that her father’s driver (Mr. Kim) is very good. She adds that her relatives have relocated to Chicago and she will check if Mr. Kim is free. They should hire him. In real Ki-Jung is making a plan for her father’s job. Ki-Taek goes to a car shop and learns the functions of new cars. Ki-Taek meets Mr. Park and hires him after a long drive.
They all get to work. They are completely unknown to each other at the time of work. Now they plan to get their mother to work in the same house. Upon further investigation, they discover that the housemaid is allergic to peaches. According to the plan, one day after the class Ki-Woo throws peach powder at Moon Gwang as he passes by, which causes him to develop an allergic reaction. She immediately goes to the hospital. The hospital, Ki-Taek reaches the hospital and takes a selfie in such a way that maid’s picture is also captured. He takes the picture in such a way her face is visible. Then the next day when he comes back from shopping, he shows Yeon-Kyo the picture and says that Moon Gwang has T.B. There are children in the house and she is roaming around the house with a deadly disease like TB. He texts Ki-Jung before going home, and just before Yeon-Kyo gets home, she drops the peach powder on her again. As Yeon-Kyo enters the room, she sees the maid coughing. Ki-Taek drops ketchup on the tissue used by the maid, causing it to bleed. Yeon-Kyo immediately removes the maid as well. On his way home from the office in the evening, Ki-Taek gives a card to Park and tells him that this company provides maids in the house of big people. Park gives the card to his wife and thus their mother also enters the house as a maid. The conditions of these people are changing now but smell a particularly foul smell from all of them. Park also mentions it to his wife. All these employees also hear this. They discuss among themselves that they have to get rid of the smell. They thought to use a new soap but they realize that the smell is not from their clothes but actually from the place where they live and they have to change their house. It’s Da-song’s birthday and they go on a picnic to celebrate. Ki-Taek family has a lot of fun in this house. Suddenly the bell rings. When they look through the monitor, the old maid of this house is standing at the door. She says that her stuff is left inside. Choong-sook tells them to hide and opens the door herself. The maid immediately goes to the kitchen. Choong-sook follows her. The maid is dragging a cupboard but there is a plate under it so the cupboard is not moving. Choong-sook removes the plate and suddenly Maid falls. There is a secret passage behind the cupboard. The maid walks into it. Choong-sook also goes there. Maid Moon Gwang is over there feeding a man. She tells Choong-sook that he is her husband who has been hiding here for the past 4 years. He had a loss in business due to which he is in debt and the debtors are finding him. Ki-Woo requests Choong-sook to keep feeding her husband, and in return, she will give her money. Choong-sook doesn’t agree and threatens to call the police. Choong-Sook’s family is hiding behind the stairs. Suddenly one of them slips and they all fall in front of the maid. As soon as she sees this, Moon Gwang immediately makes a video of them. She threatens them that she will send these videos to Yeon-Kyo, which scares them. They all come to the hall. Moon Gwang and her husband sit on the couch by themselves and ask them to sit with their hands up. Moon Gwang make their video again and also takes photos of the dining table. As soon as they get the chance, they all attack Moon Gwang and take the phone away from him. Suddenly, the house phone rings. It’s Yeon-Kyo on the phone who says that they are returning home because of the high water on the river. And they ask Choong-sook to prepare food. The family immediately tied Moon Gwang and her husband and dragged them into the basement and cleaned the house. They hide before they come. Yeon-Kyo told Choong-sook at night that on a previous birthday, Da-song was eating cake from the fridge when he saw a ghost and screamed. He got a panic attack and now he is suffering from this. (In reality, the ghost was Moon Gwang’s husband who was hiding in the basement). Children like him suffering from such a problem have to reach the hospital in 15 minutes if they are having an attack otherwise they will die.
They come home. After dinner, Da-song tells them to pitch a lawn tent outside and spend the night. Park and his wife lie down on the couch. Park talks to his wife about the musty smell coming from the driver. KI-Taek and his family are all hiding under the table listening to all this. They both love each other and fall asleep. Seeing them sleeping, these three come out from the table and run away from the house. They all run home in the pouring rain. As soon as they reach home, another trouble awaits them. Their entire house is filled with water. A window was left open and the entire house was submerged in water. They take their essentials and come to a hall where many other homeless people are also sleeping. Ki-Jung gets a call and Yeon-Kyo says that it’s Da-song birthday party and she is also invited. Da-Hye also invites Ki-Woo. Everyone is at the party. Both Ki-Woo and Da-Hye are in the room. Ki-Woo tells Da-Hye that she thinks he is one of them. Da-Hye nods yes, but Ki-Woo thinks he is not one of them. Ki-Woo thinks of the couple tied up in the basement and thinks that if they both come up, their lie can be caught. After thinking about something, he takes out his friend’s stone from his bag and goes to the basement. Arriving in the basement, Ki-Woo discovers that Moon Gwang is dead. Moon Gwang was leaving and coming up, but Choong-sook kicked her in the leg, causing her to fall down the stairs and die on the spot. Courageously, Ki-Woo moves forward. He thought that her husband would be tied but he has set himself free. He puts a rope around his neck and pulls it and ties it to the pipe. He starts to attack him with the same rock, but Ki-Woo’s rope loosens and he escapes from the basement. Suddenly the rope gets stuck and he falls to the ground. Moon Gwang’s husband attacks and injures him with the stone. Leaving him there, he comes out. There is a party going on outside. He sees Ki-Jung and immediately runs toward him. Before she can recover, he stabs her in the chest with a knife. Seeing this, Ki-Taek rushes to his daughter and puts his hand on her wound to stop the bleeding. Choong-sook sees this and immediately attacks the man and kills him. Park came near and tries to take the car keys. He puts his hand on his nose to avoid the foul smell. Ki-Taek does not like his behavior. Park takes out the car keys beneath Moon Gwang’s husband because he is unconscious. On the other hand, Ki-Taek’s daughter is dying. Unable to control himself, Ki-Taek plunges a knife into Park’s chest and disappears there.
Ki-Jung dies on the spot and due to the head injury, Ki-Woo becomes mentally ill. Park sells the house to a German couple. A case goes on against Ki-Woo and his mother but the court does not punish them but leaves them with some instructions. No one knows where Ki-Taek is. He is living in hiding in this basement. He keeps sending the signal to his son by switching the lights on and off at different times through Morse code. Finally one day his son Ki-Woo sees the signal. They both communicate with each other using the same code. Ki-Taek is saddened by Park’s death and apologizes in front of his picture in the room. Ki-Woo tells him that he will earn money by working hard and buying the same house and his father will be able to come out of this basement without any fear.
It happens. Ki-Woo buys that house Ki-Taek comes out fearlessly and meets his family but it is all his imagination and nothing like this happened.