Parasite

Ruth brought up her son Keith by herself and worked as a live-in nanny for a wealthy household, twelve years in the same house. She wanted him out of the poverty they had come from, so she put him in the basement of the family's villa and kept him there without telling anyone, feeding him while she worked upstairs. Keith grew up down there. His wants came awake and went past what a person is allowed to do, and he acted on them inside the house. Ruth covered for him. Each time she covered something she gave up another piece of what she would not do, and what she was hiding got heavier. Keith stopped keeping to the basement as well, and at one point presented himself to the household as the family's son-in-law.