An impoverished but cunning family, the Kims, live in a squalid basement apartment in Seoul. The son, Ki-woo, is offered an opportunity by a friend to take over his job as an English tutor for the wealthy Park family's daughter. The Kims see a chance to escape their dire circumstances and seize this opportunity with both hands. Ki-woo, now referred to as 'Kevin', successfully integrates himself into the Park household by forging his qualifications and impressing the Parks with his tutoring.

Ki-woo's infiltration becomes the foothold for the rest of his family to attach themselves to the Parks as well. Slowly and methodically, the Kims exploit the naivety and trust of the Parks, recommending each other for various service roles within the household. The father becomes the chauffeur, the sister an art therapy tutor, and the mother replaces the current housekeeper. As they assimilate into the Parks' daily lives, maintaining their misleading identities becomes a precarious balancing act. The Kims marvel at the luxurious lifestyle that's a stark contrast to their own, even as they must navigate the danger of their deception being exposed.