Cesar (Luis Tosar), a middle-aged man, is the manager of an apartment building. During work, he works diligently, greets every neighbor who passes by him, handles all affairs seriously, and occasionally helps residents take care of their dogs; during breaks, he goes to the hospital to visit his mother and tells her about his experiences and observations of the day. However, Cesar, who seems to be honest and introverted, has an inhumane secret. Every night, he sneaks into the room of Clara (Marta Etura), a young and beautiful female resident, and uses drugs to make her fall into a deep sleep. He sends all kinds of hot text messages to harass her on a daily basis. However, all this does not seem to be in a nearly crazy obsession, and there are deeper intentions behind his behavior. During this period, Clara's physical condition became worse and worse, and her life became a mess. In the process of his perverse behavior, everything is developing in an irreversible direction...