Three teenagers live isolated, without leaving their house, because their over-protective parents say they can only leave when their dogtooth falls out.
Three teenagers are confined to an isolated country estate that could very well be on another planet. The trio spend their days listening to endless homemade tapes that teach them a whole new vocabulary. Any word that comes from beyond their family abode is instantly assigned a new meaning. Hence 'the sea' refers to a large armchair and 'zombies' are little yellow flowers. Having invented a brother whom they claim to have ostracized for his disobedience, the über-controlling parents terrorize their offspring into submission. The father is the only family member who can leave the manicured lawns of their self-inflicted exile, earning their keep by managing a nearby factory, while the only outsider allowed on the premises is his colleague Christina, who is paid to relieve the son of his male urges. Tired of these dutiful acts of carnality, Christina disturbs the domestic balance.
Secluded from the rest of the world, confined to their affluent home and the high-walled front yard, three siblings, two sisters and one brother, are home-schooled by their parents, having no idea of life outside their prison. Within the family, the patriarch and his submissive wife give their offspring tape-recorded lessons which deliberately teach them the wrong meaning of words, further alienating them from reality. However, when the father introduces the son to Christina, a bad influence and a woman who is hired to service him sexually, the frail equilibrium of things will be disrupted with unforeseen consequences.
- The film opens with three siblings all in their late teens to early twenties in a bathroom, listening to a cassette tape. The tape contains the words they are bound to learn that day: Sea, motorway, excursion and carbine. The given definitions of all four words seem to be totally irrelevant to their real meaning. After it's finished, one of them suggests playing an endurance game involving keeping their fingers in hot water as much as they can.
Meanwhile, the father brings Christina, a female security guard he knows from work, to the house and pays her to engage in sexual intercourse with the son. The whole process feels totally forced and robotic. After they're done, he drives her back. She's blindfolded during the trips so that she won't know the location of the house.
The routine of the house gets clearer as we see from the everyday life. The children have absolutely no contact with the outside world, made believe that they cannot step outside the main gate unless they lose a dogtooth (which are in fact permanent). To pass time they help with the chores, play all kinds of endurance games and watch the video recordings of themselves. Good behaviour is awarded with stickers, while bad behaviour is punished with physical and verbal abuse. They also believe they have a brother on the other side of the fence who tried to leave before he was ready, with whom they try to communicate regularly. Only the father is allowed to leave (and only by car) to go to his work as the manager of a factory.
The father visits a dog training facility to get his dog back, only to find out that the dog's still in training and cannot be given back before it's complete.
Christina continues coming to the house but she gets frustrated when the son doesn't want to perform cunnilingus on her, so she secretly resorts to the elder daughter for sexual arousal in exchange for small gifts like a hairband. The daughter gets inspired and starts asking the same from her sister. They both seem to enjoy (unlike the son when she's with Christina) and begin doing it even when they don't have anything to trade.
One day, a stray cat gets in the garden while the father is away. Everyone is terrified until the boy manages to sneak up from behind and kill it. The father comes back with his shirt covered in fake blood, informing the family about how cats are extremely dangerous because they eat human flesh (especially children) and tells them that their brother on the other side of the fence was murdered by it. A ceremony is held for the "dead" brother.
The mother tells her husband that she's pregnant with twins. The children are not happy because they will have to share their bedrooms. The father says maybe they'll reconsider having the kids if they start behaving better.
One day, the elder daughter convinces Christina to give her the two Hollywood movie tapes in her bag, only to assure her she'll give them back the next time she comes. After she watches them, she starts reenacting scenes and quoting dialogue from the movies constantly. She also assumes the name "Bruce" (presumably because one of the movies she saw was Jaws). When the father discovers the tapes, she beats her with one of the tapes. Then she goes to Christina's apartment, hitting her in the head with the VCR, also cursing her future children to "have bad influences and develop a bad personality".
Because Christina will not be around anymore, the parents decide to let the son choose one of her sisters to become her new sexual partner. After fondling both her sisters with his eyes closed, he chooses the elder. She is extremely uncomfortable during the encounter and starts quoting threatening dialogue from the movies to his brother when they are lying in bed.
When the family is having a celebration for the wedding anniversary of the parents, they get the sisters to perform a short dance routine while the son is playing the guitar. The younger gets tired and sits, but the elder starts dancing the choreography from the movie Flashdance and seems to really enjoy it, until she is interrupted by the mother who seems really concerned.
The elder goes to the bathroom with a dumbbell and knocks out one of her dogteeth. She then sneaks outside and hides in the car's trunk. The father discovers the blood and the tooth and starts nervously looking for her outside the house. Unaware that the father stepped outside the compound on foot, violating the rules he made up, the other family members get incredibly desperate when he can't find her.
The next day, the father goes to work and leaves the car unattended in front of the factory. The frame focuses on the car's trunk, but it does not open.