Lin Wan, working overtime and living alone, returns home late at night and runs into Chen Mo, who claims to be a new resident and follows her, and then bumps into a man disguised as a food delivery worker blocking her doorway. She gets to know Su Ran, who is also being stalked, and the two discover that the maintenance worker Liu Guixiang and property manager Wu Jianfeng accepted bribes and tampered with surveillance to shield Chen Mo. The two join forces with victimized homeowners to gather evidence and call the police, and all involved personnel are punished and the residential complex completes security rectifications, but when Lin Wan takes the elevator, a new stranger suddenly blocks the elevator, and the crisis has never truly disappeared.